diff --git a/lib/formatConfig.js b/lib/formatConfig.js
deleted file mode 100644
index 376e67a8d..000000000
--- a/lib/formatConfig.js
+++ /dev/null
@@ -1,7 +0,0 @@
-module.exports = function formatConfig(config) {
-  if (typeof config === 'function') {
-    return { '*': config }
-  }
-
-  return config
-}
diff --git a/lib/generateTasks.js b/lib/generateTasks.js
index acce66364..f5c8d6cf4 100644
--- a/lib/generateTasks.js
+++ b/lib/generateTasks.js
@@ -16,39 +16,35 @@ const debug = require('debug')('lint-staged:gen-tasks')
  * @param {boolean} [options.files] - Staged filepaths
  * @param {boolean} [options.relative] - Whether filepaths to should be relative to gitDir
  */
-module.exports = function generateTasks({
-  config,
-  cwd = process.cwd(),
-  gitDir,
-  files,
-  relative = false,
-}) {
+const generateTasks = ({ config, cwd = process.cwd(), gitDir, files, relative = false }) => {
   debug('Generating linter tasks')
 
   const absoluteFiles = files.map((file) => normalize(path.resolve(gitDir, file)))
   const relativeFiles = absoluteFiles.map((file) => normalize(path.relative(cwd, file)))
 
-  return Object.entries(config).map(([pattern, commands]) => {
+  return Object.entries(config).map(([rawPattern, commands]) => {
+    let pattern = rawPattern
+
     const isParentDirPattern = pattern.startsWith('../')
 
-    const fileList = micromatch(
-      relativeFiles
-        // Only worry about children of the CWD unless the pattern explicitly
-        // specifies that it concerns a parent directory.
-        .filter((file) => {
-          if (isParentDirPattern) return true
-          return !file.startsWith('..') && !path.isAbsolute(file)
-        }),
-      pattern,
-      {
-        cwd,
-        dot: true,
-        // If pattern doesn't look like a path, enable `matchBase` to
-        // match against filenames in every directory. This makes `*.js`
-        // match both `test.js` and `subdirectory/test.js`.
-        matchBase: !pattern.includes('/'),
-      }
-    ).map((file) => normalize(relative ? file : path.resolve(cwd, file)))
+    // Only worry about children of the CWD unless the pattern explicitly
+    // specifies that it concerns a parent directory.
+    const filteredFiles = relativeFiles.filter((file) => {
+      if (isParentDirPattern) return true
+      return !file.startsWith('..') && !path.isAbsolute(file)
+    })
+
+    const matches = micromatch(filteredFiles, pattern, {
+      cwd,
+      dot: true,
+      // If the pattern doesn't look like a path, enable `matchBase` to
+      // match against filenames in every directory. This makes `*.js`
+      // match both `test.js` and `subdirectory/test.js`.
+      matchBase: !pattern.includes('/'),
+      strictBrackets: true,
+    })
+
+    const fileList = matches.map((file) => normalize(relative ? file : path.resolve(cwd, file)))
 
     const task = { pattern, commands, fileList }
     debug('Generated task: \n%O', task)
@@ -56,3 +52,5 @@ module.exports = function generateTasks({
     return task
   })
 }
+
+module.exports = generateTasks
diff --git a/lib/index.js b/lib/index.js
index a1907eff5..12ae1a19f 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,6 +1,5 @@
 'use strict'
 
-const dedent = require('dedent')
 const { cosmiconfig } = require('cosmiconfig')
 const debugLog = require('debug')('lint-staged')
 const stringifyObject = require('stringify-object')
@@ -13,9 +12,7 @@ const {
   ConfigNotFoundError,
   GetBackupStashError,
   GitError,
-  InvalidOptionsError,
 } = require('./symbols')
-const formatConfig = require('./formatConfig')
 const validateConfig = require('./validateConfig')
 const validateOptions = require('./validateOptions')
 
@@ -85,105 +82,78 @@ const lintStaged = async (
   } = {},
   logger = console
 ) => {
-  try {
-    await validateOptions({ shell }, logger)
+  await validateOptions({ shell }, logger)
 
-    debugLog('Loading config using `cosmiconfig`')
+  debugLog('Loading config using `cosmiconfig`')
 
-    const resolved = configObject
-      ? { config: configObject, filepath: '(input)' }
-      : await loadConfig(configPath)
+  const resolved = configObject
+    ? { config: configObject, filepath: '(input)' }
+    : await loadConfig(configPath)
 
-    if (resolved == null) {
-      throw ConfigNotFoundError
-    }
+  if (resolved == null) {
+    logger.error(`${ConfigNotFoundError.message}.`)
+    throw ConfigNotFoundError
+  }
 
-    debugLog('Successfully loaded config from `%s`:\n%O', resolved.filepath, resolved.config)
-
-    // resolved.config is the parsed configuration object
-    // resolved.filepath is the path to the config file that was found
-    const formattedConfig = formatConfig(resolved.config)
-    const config = validateConfig(formattedConfig)
-
-    if (debug) {
-      // Log using logger to be able to test through `consolemock`.
-      logger.log('Running lint-staged with the following config:')
-      logger.log(stringifyObject(config, { indent: '  ' }))
-    } else {
-      // We might not be in debug mode but `DEBUG=lint-staged*` could have
-      // been set.
-      debugLog('lint-staged config:\n%O', config)
-    }
+  debugLog('Successfully loaded config from `%s`:\n%O', resolved.filepath, resolved.config)
 
-    // Unset GIT_LITERAL_PATHSPECS to not mess with path interpretation
-    debugLog('Unset GIT_LITERAL_PATHSPECS (was `%s`)', process.env.GIT_LITERAL_PATHSPECS)
-    delete process.env.GIT_LITERAL_PATHSPECS
-
-    try {
-      const ctx = await runAll(
-        {
-          allowEmpty,
-          concurrent,
-          config,
-          cwd,
-          debug,
-          maxArgLength,
-          quiet,
-          relative,
-          shell,
-          stash,
-          verbose,
-        },
-        logger
-      )
-      debugLog('Tasks were executed successfully!')
-      printTaskOutput(ctx, logger)
-      return true
-    } catch (runAllError) {
-      if (runAllError && runAllError.ctx && runAllError.ctx.errors) {
-        const { ctx } = runAllError
-        if (ctx.errors.has(ApplyEmptyCommitError)) {
-          logger.warn(PREVENTED_EMPTY_COMMIT)
-        } else if (ctx.errors.has(GitError) && !ctx.errors.has(GetBackupStashError)) {
-          logger.error(GIT_ERROR)
-          if (ctx.shouldBackup) {
-            // No sense to show this if the backup stash itself is missing.
-            logger.error(RESTORE_STASH_EXAMPLE)
-          }
-        }
+  // resolved.config is the parsed configuration object
+  // resolved.filepath is the path to the config file that was found
+  const config = validateConfig(resolved.config, logger)
 
-        printTaskOutput(ctx, logger)
-        return false
-      }
+  if (debug) {
+    // Log using logger to be able to test through `consolemock`.
+    logger.log('Running lint-staged with the following config:')
+    logger.log(stringifyObject(config, { indent: '  ' }))
+  } else {
+    // We might not be in debug mode but `DEBUG=lint-staged*` could have
+    // been set.
+    debugLog('lint-staged config:\n%O', config)
+  }
 
-      // Probably a compilation error in the config js file. Pass it up to the outer error handler for logging.
-      throw runAllError
-    }
-  } catch (lintStagedError) {
-    /** throw early because `validateOptions` options contains own logging */
-    if (lintStagedError === InvalidOptionsError) {
-      throw InvalidOptionsError
-    }
+  // Unset GIT_LITERAL_PATHSPECS to not mess with path interpretation
+  debugLog('Unset GIT_LITERAL_PATHSPECS (was `%s`)', process.env.GIT_LITERAL_PATHSPECS)
+  delete process.env.GIT_LITERAL_PATHSPECS
 
-    /** @todo move logging to `validateConfig` and remove this try/catch block */
-    if (lintStagedError === ConfigNotFoundError) {
-      logger.error(`${lintStagedError.message}.`)
-    } else {
-      // It was probably a parsing error
-      logger.error(dedent`
-        Could not parse lint-staged config.
+  try {
+    const ctx = await runAll(
+      {
+        allowEmpty,
+        concurrent,
+        config,
+        cwd,
+        debug,
+        maxArgLength,
+        quiet,
+        relative,
+        shell,
+        stash,
+        verbose,
+      },
+      logger
+    )
+    debugLog('Tasks were executed successfully!')
+    printTaskOutput(ctx, logger)
+    return true
+  } catch (runAllError) {
+    if (runAllError && runAllError.ctx && runAllError.ctx.errors) {
+      const { ctx } = runAllError
+      if (ctx.errors.has(ApplyEmptyCommitError)) {
+        logger.warn(PREVENTED_EMPTY_COMMIT)
+      } else if (ctx.errors.has(GitError) && !ctx.errors.has(GetBackupStashError)) {
+        logger.error(GIT_ERROR)
+        if (ctx.shouldBackup) {
+          // No sense to show this if the backup stash itself is missing.
+          logger.error(RESTORE_STASH_EXAMPLE)
+        }
+      }
 
-        ${lintStagedError}
-      `)
+      printTaskOutput(ctx, logger)
+      return false
     }
-    logger.error() // empty line
-    // Print helpful message for all errors
-    logger.error(dedent`
-      Please make sure you have created it correctly.
-      See https://github.com/okonet/lint-staged#configuration.
-    `)
-
-    throw lintStagedError
+
+    // Probably a compilation error in the config js file. Pass it up to the outer error handler for logging.
+    throw runAllError
   }
 }
 
diff --git a/lib/makeCmdTasks.js b/lib/makeCmdTasks.js
index 1316906a6..d2706a978 100644
--- a/lib/makeCmdTasks.js
+++ b/lib/makeCmdTasks.js
@@ -3,8 +3,8 @@
 const cliTruncate = require('cli-truncate')
 const debug = require('debug')('lint-staged:make-cmd-tasks')
 
+const { configurationError } = require('./messages')
 const resolveTaskFn = require('./resolveTaskFn')
-const { createError } = require('./validateConfig')
 
 const STDOUT_COLUMNS_DEFAULT = 80
 
@@ -51,7 +51,7 @@ const makeCmdTasks = async ({ commands, files, gitDir, renderer, shell, verbose
       // Do the validation here instead of `validateConfig` to skip evaluating the function multiple times
       if (isFn && typeof command !== 'string') {
         throw new Error(
-          createError(
+          configurationError(
             '[Function]',
             'Function task should return a string or an array of strings',
             resolved
diff --git a/lib/messages.js b/lib/messages.js
index aa5b5b265..3a4f56d96 100644
--- a/lib/messages.js
+++ b/lib/messages.js
@@ -2,11 +2,26 @@
 
 const chalk = require('chalk')
 const { error, info, warning } = require('log-symbols')
+const format = require('stringify-object')
+
+const configurationError = (opt, helpMsg, value) =>
+  `${chalk.redBright(`${error} Validation Error:`)}
+
+  Invalid value for '${chalk.bold(opt)}': ${chalk.bold(
+    format(value, { inlineCharacterLimit: Number.POSITIVE_INFINITY })
+  )}
+
+  ${helpMsg}`
 
 const NOT_GIT_REPO = chalk.redBright(`${error} Current directory is not a git directory!`)
 
 const FAILED_GET_STAGED_FILES = chalk.redBright(`${error} Failed to get staged files!`)
 
+const incorrectBraces = (before, after) => `${warning} ${chalk.yellow(
+  `Detected incorrect braces with only single value: \`${before}\`. Reformatted as: \`${after}\``
+)}
+`
+
 const NO_STAGED_FILES = `${info} No staged files found.`
 
 const NO_TASKS = `${info} No staged files match any configured task.`
@@ -29,7 +44,7 @@ const GIT_ERROR = `\n  ${error} ${chalk.red(`lint-staged failed due to a git err
 
 const invalidOption = (name, value, message) => `${chalk.redBright(`${error} Validation Error:`)}
 
-  Invalid value for option ${chalk.bold(name)}: ${chalk.bold(value)}
+  Invalid value for option '${chalk.bold(name)}': ${chalk.bold(value)}
 
   ${message}
 
@@ -51,9 +66,11 @@ const CONFIG_STDIN_ERROR = 'Error: Could not read config from stdin.'
 
 module.exports = {
   CONFIG_STDIN_ERROR,
+  configurationError,
   DEPRECATED_GIT_ADD,
   FAILED_GET_STAGED_FILES,
   GIT_ERROR,
+  incorrectBraces,
   invalidOption,
   NO_STAGED_FILES,
   NO_TASKS,
diff --git a/lib/validateBraces.js b/lib/validateBraces.js
new file mode 100644
index 000000000..4d1e4868f
--- /dev/null
+++ b/lib/validateBraces.js
@@ -0,0 +1,71 @@
+const { incorrectBraces } = require('./messages')
+
+/**
+ * A correctly-formed brace expansion must contain unquoted opening and closing braces,
+ * and at least one unquoted comma or a valid sequence expression.
+ * Any incorrectly formed brace expansion is left unchanged.
+ *
+ * @see https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html
+ *
+ * Lint-staged uses `micromatch` for brace expansion, and its behavior is to treat
+ * invalid brace expansions as literal strings, which means they (typically) do not match
+ * anything.
+ *
+ * This RegExp tries to match most cases of invalid brace expansions, so that they can be
+ * detected, warned about, and re-formatted by removing the braces and thus hopefully
+ * matching the files as intended by the user. The only real fix is to remove the incorrect
+ * braces from user configuration, but this is left to the user (after seeing the warning).
+ *
+ * @example <caption>Globs with brace expansions</caption>
+ * - *.{js,tx}         // expanded as *.js, *.ts
+ * - *.{{j,t}s,css}    // expanded as *.js, *.ts, *.css
+ * - file_{1..10}.css  // expanded as file_1.css, file_2.css, …, file_10.css
+ *
+ * @example <caption>Globs with incorrect brace expansions</caption>
+ * - *.{js}       // should just be *.js
+ * - *.{js,{ts}}  // should just be *.{js,ts}
+ * - *.\{js\}     // escaped braces, so they're treated literally
+ * - *.${js}      // dollar-sign inhibits expansion, so treated literally
+ * - *.{js\,ts}   // the comma is escaped, so treated literally
+ */
+const BRACES_REGEXP = /(?<![\\$])({)(?:(?!(?<!\\),|\.\.|\{|\}).)*?(?<!\\)(})/g
+
+/**
+ * @param {string} pattern
+ * @returns {string}
+ */
+const withoutIncorrectBraces = (pattern) => {
+  let output = `${pattern}`
+  let match = null
+
+  while ((match = BRACES_REGEXP.exec(pattern))) {
+    const fullMatch = match[0]
+    const withoutBraces = fullMatch.replace(/{/, '').replace(/}/, '')
+    output = output.replace(fullMatch, withoutBraces)
+  }
+
+  return output
+}
+
+/**
+ * Validate and remove incorrect brace expansions from glob pattern.
+ * For example `*.{js}` is incorrect because it doesn't contain a `,` or `..`,
+ * and will be reformatted as `*.js`.
+ *
+ * @param {string} pattern the glob pattern
+ * @param {*} logger
+ * @returns {string}
+ */
+const validateBraces = (pattern, logger) => {
+  const fixedPattern = withoutIncorrectBraces(pattern)
+
+  if (fixedPattern !== pattern) {
+    logger.warn(incorrectBraces(pattern, fixedPattern))
+  }
+
+  return fixedPattern
+}
+
+module.exports = validateBraces
+
+module.exports.BRACES_REGEXP = BRACES_REGEXP
diff --git a/lib/validateConfig.js b/lib/validateConfig.js
index 0e34ef930..a5c46facb 100644
--- a/lib/validateConfig.js
+++ b/lib/validateConfig.js
@@ -2,11 +2,11 @@
 
 'use strict'
 
-const chalk = require('chalk')
-const format = require('stringify-object')
-
 const debug = require('debug')('lint-staged:cfg')
 
+const { configurationError } = require('./messages')
+const validateBraces = require('./validateBraces')
+
 const TEST_DEPRECATED_KEYS = new Map([
   ['concurrent', (key) => typeof key === 'boolean'],
   ['chunkSize', (key) => typeof key === 'number'],
@@ -18,76 +18,91 @@ const TEST_DEPRECATED_KEYS = new Map([
   ['relative', (key) => typeof key === 'boolean'],
 ])
 
-const formatError = (helpMsg) => `● Validation Error:
-
-  ${helpMsg}
-
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...`
-
-const createError = (opt, helpMsg, value) =>
-  formatError(`Invalid value for '${chalk.bold(opt)}'.
-
-  ${helpMsg}.
- 
-  Configured value is: ${chalk.bold(
-    format(value, { inlineCharacterLimit: Number.POSITIVE_INFINITY })
-  )}`)
-
 /**
  * Runs config validation. Throws error if the config is not valid.
  * @param config {Object}
  * @returns config {Object}
  */
-module.exports = function validateConfig(config) {
+const validateConfig = (config, logger) => {
   debug('Validating config')
 
-  const errors = []
+  if (!config || (typeof config !== 'object' && typeof config !== 'function')) {
+    throw new Error('Configuration should be an object or a function!')
+  }
 
-  if (!config || typeof config !== 'object') {
-    errors.push('Configuration should be an object!')
-  } else {
-    const entries = Object.entries(config)
+  /**
+   * Function configurations receive all staged files as their argument.
+   * They are not further validated here to make sure the function gets
+   * evaluated only once.
+   *
+   * @see makeCmdTasks
+   */
+  if (typeof config === 'function') {
+    return { '*': config }
+  }
 
-    if (entries.length === 0) {
-      errors.push('Configuration should not be empty!')
-    }
+  if (Object.entries(config).length === 0) {
+    throw new Error('Configuration should not be empty!')
+  }
 
-    entries.forEach(([pattern, task]) => {
-      if (TEST_DEPRECATED_KEYS.has(pattern)) {
-        const testFn = TEST_DEPRECATED_KEYS.get(pattern)
-        if (testFn(task)) {
-          errors.push(
-            createError(
-              pattern,
-              'Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged',
-              task
-            )
-          )
-        }
-      }
+  const errors = []
 
-      if (
-        (!Array.isArray(task) ||
-          task.some((item) => typeof item !== 'string' && typeof item !== 'function')) &&
-        typeof task !== 'string' &&
-        typeof task !== 'function'
-      ) {
+  /**
+   * Create a new validated config because the keys (patterns) might change.
+   * Since the Object.reduce method already loops through each entry in the config,
+   * it can be used for validating the values at the same time.
+   */
+  const validatedConfig = Object.entries(config).reduce((collection, [pattern, task]) => {
+    /** Versions < 9 had more complex configuration options that are no longer supported. */
+    if (TEST_DEPRECATED_KEYS.has(pattern)) {
+      const testFn = TEST_DEPRECATED_KEYS.get(pattern)
+      if (testFn(task)) {
         errors.push(
-          createError(
-            pattern,
-            'Should be a string, a function, or an array of strings and functions',
-            task
-          )
+          configurationError(pattern, 'Advanced configuration has been deprecated.', task)
         )
       }
-    })
-  }
+
+      /** Return early for deprecated keys to skip validating their (deprecated) values */
+      return collection
+    }
+
+    if (
+      (!Array.isArray(task) ||
+        task.some((item) => typeof item !== 'string' && typeof item !== 'function')) &&
+      typeof task !== 'string' &&
+      typeof task !== 'function'
+    ) {
+      errors.push(
+        configurationError(
+          pattern,
+          'Should be a string, a function, or an array of strings and functions.',
+          task
+        )
+      )
+    }
+
+    /**
+     * A typical configuration error is using invalid brace expansion, like `*.{js}`.
+     * These are automatically fixed and warned about.
+     */
+    const fixedPattern = validateBraces(pattern, logger)
+
+    return { ...collection, [fixedPattern]: task }
+  }, {})
 
   if (errors.length) {
-    throw new Error(errors.join('\n'))
+    const message = errors.join('\n\n')
+
+    logger.error(`Could not parse lint-staged config.
+
+${message}
+
+See https://github.com/okonet/lint-staged#configuration.`)
+
+    throw new Error(message)
   }
 
-  return config
+  return validatedConfig
 }
 
-module.exports.createError = createError
+module.exports = validateConfig
diff --git a/package.json b/package.json
index dba20462d..d90e45abc 100644
--- a/package.json
+++ b/package.json
@@ -32,7 +32,6 @@
     "commander": "^7.2.0",
     "cosmiconfig": "^7.0.0",
     "debug": "^4.3.1",
-    "dedent": "^0.7.0",
     "enquirer": "^2.3.6",
     "execa": "^5.0.0",
     "listr2": "^3.8.2",
diff --git a/test/__snapshots__/index2.spec.js.snap b/test/__snapshots__/index2.spec.js.snap
deleted file mode 100644
index 0a25f136a..000000000
--- a/test/__snapshots__/index2.spec.js.snap
+++ /dev/null
@@ -1,11 +0,0 @@
-// Jest Snapshot v1, https://goo.gl/fbAQLP
-
-exports[`lintStaged should catch errors from js function config 2`] = `
-"
-ERROR Could not parse lint-staged config.
-
-Error: failed config
-ERROR 
-ERROR Please make sure you have created it correctly.
-See https://github.com/okonet/lint-staged#configuration."
-`;
diff --git a/test/__snapshots__/validateConfig.spec.js.snap b/test/__snapshots__/validateConfig.spec.js.snap
index c58ec222b..50d62fe66 100644
--- a/test/__snapshots__/validateConfig.spec.js.snap
+++ b/test/__snapshots__/validateConfig.spec.js.snap
@@ -1,154 +1,116 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`validateConfig should not throw and should print nothing for function config 1`] = `""`;
+exports[`validateConfig should throw and should print validation errors for invalid config 1`] = `
+"× Validation Error:
 
-exports[`validateConfig should not throw and should print nothing for function task 1`] = `""`;
+  Invalid value for 'foo': false
 
-exports[`validateConfig should not throw and should print nothing for valid config 1`] = `""`;
+  Should be a string, a function, or an array of strings and functions."
+`;
 
-exports[`validateConfig should not throw when config contains deprecated key but with valid task 1`] = `""`;
+exports[`validateConfig should throw and should print validation errors for invalid config 1 1`] = `"Configuration should be an object or a function!"`;
 
-exports[`validateConfig should throw and should print validation errors for invalid config 1`] = `
-"● Validation Error:
+exports[`validateConfig should throw when detecting deprecated advanced configuration 1`] = `
+"× Validation Error:
 
-  Invalid value for 'foo'.
+  Invalid value for 'chunkSize': 10
 
-  Should be a string, a function, or an array of strings and functions.
- 
-  Configured value is: false
+  Advanced configuration has been deprecated.
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information..."
-`;
+× Validation Error:
 
-exports[`validateConfig should throw and should print validation errors for invalid config 1 1`] = `"Configuration should be an object!"`;
+  Invalid value for 'concurrent': false
 
-exports[`validateConfig should throw when detecting deprecated advanced configuration 1`] = `
-"● Validation Error:
+  Advanced configuration has been deprecated.
 
-  Invalid value for 'chunkSize'.
+× Validation Error:
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: 10
+  Invalid value for 'globOptions': {matchBase: false}
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Advanced configuration has been deprecated.
 
-  Invalid value for 'chunkSize'.
+× Validation Error:
 
-  Should be a string, a function, or an array of strings and functions.
- 
-  Configured value is: 10
+  Invalid value for 'ignore': ['test.js']
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Advanced configuration has been deprecated.
 
-  Invalid value for 'concurrent'.
+× Validation Error:
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: false
+  Invalid value for 'linters': {'*.js': ['eslint']}
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Advanced configuration has been deprecated.
 
-  Invalid value for 'concurrent'.
+× Validation Error:
 
-  Should be a string, a function, or an array of strings and functions.
- 
-  Configured value is: false
+  Invalid value for 'relative': true
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Advanced configuration has been deprecated.
 
-  Invalid value for 'globOptions'.
+× Validation Error:
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: {matchBase: false}
+  Invalid value for 'renderer': 'silent'
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Advanced configuration has been deprecated.
 
-  Invalid value for 'globOptions'.
+× Validation Error:
 
-  Should be a string, a function, or an array of strings and functions.
- 
-  Configured value is: {matchBase: false}
+  Invalid value for 'subTaskConcurrency': 10
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Advanced configuration has been deprecated."
+`;
 
-  Invalid value for 'ignore'.
+exports[`validateConfig should throw when detecting deprecated advanced configuration 2`] = `
+"
+ERROR Could not parse lint-staged config.
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: ['test.js']
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Invalid value for 'chunkSize': 10
 
-  Invalid value for 'linters'.
+  Advanced configuration has been deprecated.
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: {'*.js': ['eslint']}
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Invalid value for 'concurrent': false
 
-  Invalid value for 'linters'.
+  Advanced configuration has been deprecated.
 
-  Should be a string, a function, or an array of strings and functions.
- 
-  Configured value is: {'*.js': ['eslint']}
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Invalid value for 'globOptions': {matchBase: false}
 
-  Invalid value for 'relative'.
+  Advanced configuration has been deprecated.
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: true
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Invalid value for 'ignore': ['test.js']
 
-  Invalid value for 'relative'.
+  Advanced configuration has been deprecated.
 
-  Should be a string, a function, or an array of strings and functions.
- 
-  Configured value is: true
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Invalid value for 'linters': {'*.js': ['eslint']}
 
-  Invalid value for 'renderer'.
+  Advanced configuration has been deprecated.
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: 'silent'
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Invalid value for 'relative': true
 
-  Invalid value for 'subTaskConcurrency'.
+  Advanced configuration has been deprecated.
 
-  Advanced configuration has been deprecated. For more info, please visit: https://github.com/okonet/lint-staged.
- 
-  Configured value is: 10
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information...
-● Validation Error:
+  Invalid value for 'renderer': 'silent'
 
-  Invalid value for 'subTaskConcurrency'.
+  Advanced configuration has been deprecated.
 
-  Should be a string, a function, or an array of strings and functions.
- 
-  Configured value is: 10
+× Validation Error:
 
-Please refer to https://github.com/okonet/lint-staged#configuration for more information..."
-`;
+  Invalid value for 'subTaskConcurrency': 10
 
-exports[`validateConfig should throw when detecting deprecated advanced configuration 2`] = `""`;
+  Advanced configuration has been deprecated.
+
+See https://github.com/okonet/lint-staged#configuration."
+`;
diff --git a/test/formatConfig.spec.js b/test/formatConfig.spec.js
deleted file mode 100644
index 903ce56d2..000000000
--- a/test/formatConfig.spec.js
+++ /dev/null
@@ -1,17 +0,0 @@
-import formatConfig from '../lib/formatConfig'
-
-describe('formatConfig', () => {
-  it('Object config should return as is', () => {
-    const simpleConfig = {
-      '*.js': ['eslint --fix', 'git add'],
-    }
-    expect(formatConfig(simpleConfig)).toEqual(simpleConfig)
-  })
-
-  it('Function config should be converted to object', () => {
-    const functionConfig = (stagedFiles) => [`eslint --fix ${stagedFiles}', 'git add`]
-    expect(formatConfig(functionConfig)).toEqual({
-      '*': functionConfig,
-    })
-  })
-})
diff --git a/test/generateTasks.spec.js b/test/generateTasks.spec.js
index d2f9540f0..fd068dad2 100644
--- a/test/generateTasks.spec.js
+++ b/test/generateTasks.spec.js
@@ -1,5 +1,5 @@
-import os from 'os'
 import normalize from 'normalize-path'
+import os from 'os'
 import path from 'path'
 
 import generateTasks from '../lib/generateTasks'
@@ -15,7 +15,7 @@ const files = [
   '.hidden/test.js',
 
   'test.css',
-  'deeper/test.css',
+  'deeper/test1.css',
   'deeper/test2.css',
   'even/deeper/test.css',
   '.hidden/test.css',
@@ -145,7 +145,7 @@ describe('generateTasks', () => {
         `${gitDir}/even/deeper/test.js`,
         `${gitDir}/.hidden/test.js`,
         `${gitDir}/test.css`,
-        `${gitDir}/deeper/test.css`,
+        `${gitDir}/deeper/test1.css`,
         `${gitDir}/deeper/test2.css`,
         `${gitDir}/even/deeper/test.css`,
         `${gitDir}/.hidden/test.css`,
@@ -153,6 +153,25 @@ describe('generateTasks', () => {
     })
   })
 
+  it('should match pattern "test{1..2}.css"', async () => {
+    const result = await generateTasks({
+      config: {
+        'test{1..2}.css': 'lint',
+      },
+      cwd,
+      gitDir,
+      files,
+    })
+
+    const linter = result.find((item) => item.pattern === 'test{1..2}.css')
+
+    expect(linter).toEqual({
+      pattern: 'test{1..2}.css',
+      commands: 'lint',
+      fileList: [`${gitDir}/deeper/test1.css`, `${gitDir}/deeper/test2.css`].map(normalizePath),
+    })
+  })
+
   it('should not match files in parent directory by default', async () => {
     const result = await generateTasks({
       config,
@@ -196,7 +215,7 @@ describe('generateTasks', () => {
         'even/deeper/test.js',
         '.hidden/test.js',
         'test.css',
-        'deeper/test.css',
+        'deeper/test1.css',
         'deeper/test2.css',
         'even/deeper/test.css',
         '.hidden/test.css',
diff --git a/test/index.spec.js b/test/index.spec.js
index 6a98a629a..047e528e3 100644
--- a/test/index.spec.js
+++ b/test/index.spec.js
@@ -70,15 +70,7 @@ describe('lintStaged', () => {
       `[Error: Configuration should not be empty!]`
     )
 
-    expect(mockedConsole.printHistory()).toMatchInlineSnapshot(`
-      "
-      ERROR Could not parse lint-staged config.
-
-      Error: Configuration should not be empty!
-      ERROR 
-      ERROR Please make sure you have created it correctly.
-      See https://github.com/okonet/lint-staged#configuration."
-    `)
+    expect(mockedConsole.printHistory()).toMatchInlineSnapshot(`""`)
 
     console = previousConsole
   })
@@ -133,15 +125,7 @@ describe('lintStaged', () => {
       `[Error: Configuration should not be empty!]`
     )
 
-    expect(logger.printHistory()).toMatchInlineSnapshot(`
-      "
-      ERROR Could not parse lint-staged config.
-
-      Error: Configuration should not be empty!
-      ERROR 
-      ERROR Please make sure you have created it correctly.
-      See https://github.com/okonet/lint-staged#configuration."
-    `)
+    expect(logger.printHistory()).toMatchInlineSnapshot(`""`)
   })
 
   it('should load config file when specified', async () => {
@@ -224,10 +208,7 @@ describe('lintStaged', () => {
 
     expect(logger.printHistory()).toMatchInlineSnapshot(`
       "
-      ERROR Config could not be found.
-      ERROR 
-      ERROR Please make sure you have created it correctly.
-      See https://github.com/okonet/lint-staged#configuration."
+      ERROR Config could not be found."
     `)
   })
 
@@ -239,8 +220,8 @@ describe('lintStaged', () => {
     // Serialize Windows, Linux and MacOS paths consistently
     expect.addSnapshotSerializer(
       replaceSerializer(
-        /Error: ENOENT: no such file or directory, open '([^']+)'/,
-        `Error: ENOENT: no such file or directory, open '${nonExistentConfig}'`
+        /ENOENT: no such file or directory, open '([^']+)'/,
+        `ENOENT: no such file or directory, open '${nonExistentConfig}'`
       )
     )
 
@@ -248,14 +229,6 @@ describe('lintStaged', () => {
       lintStaged({ configPath: nonExistentConfig, quiet: true }, logger)
     ).rejects.toThrowError()
 
-    expect(logger.printHistory()).toMatchInlineSnapshot(`
-
-      ERROR Could not parse lint-staged config.
-
-      Error: ENOENT: no such file or directory, open 'fake-config-file.yml'
-      ERROR 
-      ERROR Please make sure you have created it correctly.
-      See https://github.com/okonet/lint-staged#configuration.
-    `)
+    expect(logger.printHistory()).toMatchInlineSnapshot(`""`)
   })
 })
diff --git a/test/index2.spec.js b/test/index2.spec.js
index bdeafcbfe..625623a6b 100644
--- a/test/index2.spec.js
+++ b/test/index2.spec.js
@@ -77,6 +77,7 @@ describe('lintStaged', () => {
     await expect(lintStaged({ config }, logger)).rejects.toThrowErrorMatchingInlineSnapshot(
       `"failed config"`
     )
-    expect(logger.printHistory()).toMatchSnapshot()
+
+    expect(logger.printHistory()).toMatchInlineSnapshot(`""`)
   })
 })
diff --git a/test/makeCmdTasks.spec.js b/test/makeCmdTasks.spec.js
index bdb7a1522..d215c224c 100644
--- a/test/makeCmdTasks.spec.js
+++ b/test/makeCmdTasks.spec.js
@@ -109,16 +109,12 @@ describe('makeCmdTasks', () => {
   it("should throw when function task doesn't return string | string[]", async () => {
     await expect(makeCmdTasks({ commands: () => null, gitDir, files: ['test.js'] })).rejects
       .toThrowErrorMatchingInlineSnapshot(`
-"● Validation Error:
+            "× Validation Error:
 
-  Invalid value for '[Function]'.
+              Invalid value for '[Function]': null
 
-  Function task should return a string or an array of strings.
- 
-  Configured value is: null
-
-Please refer to https://github.com/okonet/lint-staged#configuration for more information..."
-`)
+              Function task should return a string or an array of strings"
+          `)
   })
 
   it('should truncate task title', async () => {
diff --git a/test/validateBraces.spec.js b/test/validateBraces.spec.js
new file mode 100644
index 000000000..11168abdb
--- /dev/null
+++ b/test/validateBraces.spec.js
@@ -0,0 +1,124 @@
+import makeConsoleMock from 'consolemock'
+
+import validateBraces, { BRACES_REGEXP } from '../lib/validateBraces'
+
+describe('BRACES_REGEXP', () => {
+  it(`should match '*.{js}'`, () => {
+    expect('*.{js}'.match(BRACES_REGEXP)).toBeTruthy()
+  })
+
+  it(`should match 'file_{10}'`, () => {
+    expect('file_{test}'.match(BRACES_REGEXP)).toBeTruthy()
+  })
+
+  it(`should match '*.{spec\\.js}'`, () => {
+    expect('*.{spec\\.js}'.match(BRACES_REGEXP)).toBeTruthy()
+  })
+
+  it(`should match '*.{js\\,ts}'`, () => {
+    expect('*.{js\\,ts}'.match(BRACES_REGEXP)).toBeTruthy()
+  })
+
+  it("should not match '*.${js}'", () => {
+    expect('*.${js}'.match(BRACES_REGEXP)).not.toBeTruthy()
+  })
+
+  it(`should not match '.{js,ts}'`, () => {
+    expect('.{js,ts}'.match(BRACES_REGEXP)).not.toBeTruthy()
+  })
+
+  it(`should not match 'file_{1..10}'`, () => {
+    expect('file_{1..10}'.match(BRACES_REGEXP)).not.toBeTruthy()
+  })
+
+  it(`should not match '*.\\{js\\}'`, () => {
+    expect('*.\\{js\\}'.match(BRACES_REGEXP)).not.toBeTruthy()
+  })
+
+  it(`should not match '*.\\{js}'`, () => {
+    expect('*.\\{js}'.match(BRACES_REGEXP)).not.toBeTruthy()
+  })
+
+  it(`should not match '*.{js\\}'`, () => {
+    expect('*.{js\\}'.match(BRACES_REGEXP)).not.toBeTruthy()
+  })
+})
+
+describe('validateBraces', () => {
+  it('should warn about `*.{js}` and return fixed pattern', () => {
+    const logger = makeConsoleMock()
+
+    const fixedBraces = validateBraces('*.{js}', logger)
+
+    expect(fixedBraces).toEqual('*.js')
+    expect(logger.printHistory()).toMatchInlineSnapshot(`
+      "
+      WARN ‼ Detected incorrect braces with only single value: \`*.{js}\`. Reformatted as: \`*.js\`
+      "
+    `)
+  })
+
+  it('should warn about `*.{ts}{x}` and return fixed pattern', () => {
+    const logger = makeConsoleMock()
+
+    const fixedBraces = validateBraces('*.{ts}{x}', logger)
+
+    expect(fixedBraces).toEqual('*.tsx')
+    expect(logger.printHistory()).toMatchInlineSnapshot(`
+      "
+      WARN ‼ Detected incorrect braces with only single value: \`*.{ts}{x}\`. Reformatted as: \`*.tsx\`
+      "
+    `)
+  })
+
+  it('should warn about `*.{js,{ts}}` and return fixed pattern', () => {
+    const logger = makeConsoleMock()
+
+    const fixedBraces = validateBraces('*.{js,{ts}}', logger)
+
+    expect(fixedBraces).toEqual('*.{js,ts}')
+    expect(logger.printHistory()).toMatchInlineSnapshot(`
+      "
+      WARN ‼ Detected incorrect braces with only single value: \`*.{js,{ts}}\`. Reformatted as: \`*.{js,ts}\`
+      "
+    `)
+  })
+
+  /**
+   * @todo This isn't correctly detected even though the outer braces are invalid.
+   */
+  it.skip('should warn about `*.{{js,ts}}` and return fixed pattern', () => {
+    const logger = makeConsoleMock()
+
+    const fixedBraces = validateBraces('*.{{js,ts}}', logger)
+
+    expect(fixedBraces).toEqual('*.{js,ts}')
+    expect(logger.printHistory()).toMatchInlineSnapshot(`
+      "
+      WARN ‼ Detected incorrect braces with only single value: \`*.{{js,ts}}\`. Reformatted as: \`*.{js,ts}\`
+      "
+    `)
+  })
+
+  it('should warn about `*.{{js,ts},{css}}` and return fixed pattern', () => {
+    const logger = makeConsoleMock()
+
+    const fixedBraces = validateBraces('*.{{js,ts},{css}}', logger)
+
+    expect(fixedBraces).toEqual('*.{{js,ts},css}')
+    expect(logger.printHistory()).toMatchInlineSnapshot(`
+      "
+      WARN ‼ Detected incorrect braces with only single value: \`*.{{js,ts},{css}}\`. Reformatted as: \`*.{{js,ts},css}\`
+      "
+    `)
+  })
+
+  it('should not warn about `*.\\{js\\}` and return the same pattern', () => {
+    const logger = makeConsoleMock()
+
+    const fixedBraces = validateBraces('*.\\{js\\}', logger)
+
+    expect(fixedBraces).toEqual('*.\\{js\\}')
+    expect(logger.printHistory()).toMatchInlineSnapshot(`""`)
+  })
+})
diff --git a/test/validateConfig.spec.js b/test/validateConfig.spec.js
index bf6d4a0f2..66376e9d6 100644
--- a/test/validateConfig.spec.js
+++ b/test/validateConfig.spec.js
@@ -2,59 +2,56 @@ import makeConsoleMock from 'consolemock'
 
 import validateConfig from '../lib/validateConfig'
 
-import formatConfig from '../lib/formatConfig'
-
 describe('validateConfig', () => {
-  const originalConsole = global.console
-  beforeAll(() => {
-    global.console = makeConsoleMock()
-  })
+  let logger
 
   beforeEach(() => {
-    global.console.clearHistory()
-  })
-
-  afterAll(() => {
-    global.console = originalConsole
+    logger = makeConsoleMock()
   })
 
   it('should throw and should print validation errors for invalid config 1', () => {
     const invalidConfig = 'test'
-    expect(() => validateConfig(invalidConfig)).toThrowErrorMatchingSnapshot()
+
+    expect(() => validateConfig(invalidConfig, logger)).toThrowErrorMatchingSnapshot()
   })
 
   it('should throw and should print validation errors for invalid config', () => {
     const invalidConfig = {
       foo: false,
     }
-    expect(() => validateConfig(invalidConfig)).toThrowErrorMatchingSnapshot()
+
+    expect(() => validateConfig(invalidConfig, logger)).toThrowErrorMatchingSnapshot()
+  })
+
+  it('should wrap function config into object', () => {
+    const functionConfig = (stagedFiles) => [`eslint --fix ${stagedFiles}', 'git add`]
+
+    expect(validateConfig(functionConfig, logger)).toEqual({
+      '*': functionConfig,
+    })
+    expect(logger.printHistory()).toEqual('')
   })
 
   it('should not throw and should print nothing for valid config', () => {
     const validSimpleConfig = {
       '*.js': ['eslint --fix', 'git add'],
     }
-    expect(() => validateConfig(validSimpleConfig)).not.toThrow()
-    expect(console.printHistory()).toMatchSnapshot()
-  })
 
-  it('should not throw and should print nothing for function config', () => {
-    const functionConfig = (stagedFiles) => [`eslint ${stagedFiles.join(' ')}`]
-    expect(() => validateConfig(formatConfig(functionConfig))).not.toThrow()
-    expect(console.printHistory()).toMatchSnapshot()
+    expect(() => validateConfig(validSimpleConfig, logger)).not.toThrow()
+    expect(logger.printHistory()).toEqual('')
   })
 
   it('should not throw and should print nothing for function task', () => {
-    expect(() =>
-      validateConfig({
-        '*.js': (filenames) => {
-          const files = filenames.join(' ')
-          return `eslint --fix ${files} && git add ${files}`
-        },
-        '*.css': [(filenames) => filenames.map((filename) => `eslint --fix ${filename}`)],
-      })
-    ).not.toThrow()
-    expect(console.printHistory()).toMatchSnapshot()
+    const functionTask = {
+      '*.js': (filenames) => {
+        const files = filenames.join(' ')
+        return `eslint --fix ${files} && git add ${files}`
+      },
+      '*.css': [(filenames) => filenames.map((filename) => `eslint --fix ${filename}`)],
+    }
+
+    expect(() => validateConfig(functionTask, logger)).not.toThrow()
+    expect(logger.printHistory()).toEqual('')
   })
 
   it('should throw when detecting deprecated advanced configuration', () => {
@@ -71,15 +68,16 @@ describe('validateConfig', () => {
       subTaskConcurrency: 10,
     }
 
-    expect(() => validateConfig(advancedConfig)).toThrowErrorMatchingSnapshot()
-    expect(console.printHistory()).toMatchSnapshot()
+    expect(() => validateConfig(advancedConfig, logger)).toThrowErrorMatchingSnapshot()
+    expect(logger.printHistory()).toMatchSnapshot()
   })
 
   it('should not throw when config contains deprecated key but with valid task', () => {
     const stillValidConfig = {
       concurrent: 'my command',
     }
-    expect(() => validateConfig(stillValidConfig)).not.toThrow()
-    expect(console.printHistory()).toMatchSnapshot()
+
+    expect(() => validateConfig(stillValidConfig, logger)).not.toThrow()
+    expect(logger.printHistory()).toEqual('')
   })
 })
diff --git a/test/validateOptions.spec.js b/test/validateOptions.spec.js
index a888e4d8e..45acc6d72 100644
--- a/test/validateOptions.spec.js
+++ b/test/validateOptions.spec.js
@@ -41,7 +41,7 @@ describe('validateOptions', () => {
 
     const logger = makeConsoleMock()
 
-    mockAccess.mockImplementationOnce(() => new Promise.reject())
+    mockAccess.mockImplementationOnce(() => Promise.reject(new Error('Failed')))
 
     await expect(validateOptions({ shell: '/bin/sh' }, logger)).rejects.toThrowError(
       InvalidOptionsError
@@ -55,9 +55,9 @@ describe('validateOptions', () => {
       "
       ERROR × Validation Error:
 
-        Invalid value for option shell: /bin/sh
+        Invalid value for option 'shell': /bin/sh
 
-        Promise.reject is not a constructor
+        Failed
 
       See https://github.com/okonet/lint-staged#command-line-flags"
     `)
diff --git a/yarn.lock b/yarn.lock
index dad17a326..f86131fd9 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2490,11 +2490,6 @@ decode-uri-component@^0.2.0:
   resolved "https://registry.yarnpkg.com/decode-uri-component/-/decode-uri-component-0.2.0.tgz#eb3913333458775cb84cd1a1fae062106bb87545"
   integrity sha1-6zkTMzRYd1y4TNGh+uBiEGu4dUU=
 
-dedent@^0.7.0:
-  version "0.7.0"
-  resolved "https://registry.yarnpkg.com/dedent/-/dedent-0.7.0.tgz#2495ddbaf6eb874abb0e1be9df22d2e5a544326c"
-  integrity sha1-JJXduvbrh0q7Dhvp3yLS5aVEMmw=
-
 deep-is@^0.1.3, deep-is@~0.1.3:
   version "0.1.3"
   resolved "https://registry.yarnpkg.com/deep-is/-/deep-is-0.1.3.tgz#b369d6fb5dbc13eecf524f91b070feedc357cf34"