diff --git a/README.md b/README.md
index 2f0c55bc..63f5eb62 100644
--- a/README.md
+++ b/README.md
@@ -79,12 +79,6 @@ All of the arguments are optional:
 
 `--parsers`, `--detectors` and `--specials`: These arguments are for advanced usage. They provide an easy way to customize the file parser and dependency detection. Check [the pluggable design document](https://github.com/depcheck/depcheck/blob/master/doc/pluggable-design.md) for more information.
 
-### Deprecated arguments
-
-The following arguments are deprecated and will be removed in next major version:
-
-`--dev=[true|false]`: *[DEPRECATED]* It leads a wrong result for missing dependencies when it is `false`. This option will be enforced to `true` in next major version. The corresponding API option `withoutDev` is deprecated too.
-
 ## API
 
 Similar options are provided to `depcheck` function for programming:
@@ -93,7 +87,6 @@ Similar options are provided to `depcheck` function for programming:
 import depcheck from 'depcheck';
 
 const options = {
-  withoutDev: false, // [DEPRECATED] check against devDependencies
   ignoreBinPackage: false, // ignore the packages with bin entry
   skipMissing: false, // skip calculation of missing dependencies
   ignoreDirs: [ // folder with these names will be ignored
diff --git a/doc/pluggable-design.md b/doc/pluggable-design.md
index 68b3e60f..83cffb39 100644
--- a/doc/pluggable-design.md
+++ b/doc/pluggable-design.md
@@ -148,7 +148,7 @@ var opts = {
 
 ### Implement Custom Detector
 
-Detector is a JavaScript function accepts an AST node and package dependencies (including devDependencies unless `withoutDev` option is `true`) and returns an array of dependency package names.
+Detector is a JavaScript function accepts an AST node and package dependencies and returns an array of dependency package names.
 
 The following code snippet is the ES6 `import` declaration detector:
 
@@ -228,7 +228,7 @@ As seen from the code snippet, there are four parameters passed into the *specia
 
 - Content, same as normal parser, the file content.
 - FilePath, the file path, use `path.basename` to retrieve the file name.
-- Deps, an array containing the package dependencies (including devDependencies unless `withoutDev` option is `true`).
+- Deps, an array containing the package dependencies.
 - Dir, the checking root directory passed from API or CLI.
 
 Pay attention that, special parser will match **all** files, please do file path or file name matching **by yourself** and only parse content only when necessary. In regards to the returning value, both AST node or plain string array are OK as a normal parser.
diff --git a/package-lock.json b/package-lock.json
index 07fd7f39..51ece248 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2072,11 +2072,6 @@
         }
       }
     },
-    "deprecate": {
-      "version": "1.1.1",
-      "resolved": "https://registry.npmjs.org/deprecate/-/deprecate-1.1.1.tgz",
-      "integrity": "sha512-ZGDXefq1xknT292LnorMY5s8UVU08/WKdzDZCUT6t9JzsiMSP4uzUhgpqugffNVcT5WC6wMBiSQ+LFjlv3v7iQ=="
-    },
     "deps-regex": {
       "version": "0.1.4",
       "resolved": "https://registry.npmjs.org/deps-regex/-/deps-regex-0.1.4.tgz",
diff --git a/package.json b/package.json
index 982f1800..8bacbe12 100644
--- a/package.json
+++ b/package.json
@@ -50,7 +50,6 @@
     "@babel/parser": "^7.6.4",
     "@babel/traverse": "^7.6.3",
     "builtin-modules": "^3.0.0",
-    "deprecate": "^1.1.1",
     "deps-regex": "^0.1.4",
     "js-yaml": "^3.4.2",
     "lodash": "^4.17.15",
diff --git a/src/cli.js b/src/cli.js
index 51ab6317..d9dca006 100755
--- a/src/cli.js
+++ b/src/cli.js
@@ -2,7 +2,6 @@ import fs from 'fs';
 import path from 'path';
 import yargs from 'yargs';
 import lodash from 'lodash';
-import deprecate from 'deprecate';
 
 import depcheck from './index';
 import { version } from '../package.json';
@@ -68,17 +67,6 @@ function print(result, log, json, rootDir) {
   return result;
 }
 
-function checkDeprecation(argv) {
-  if (argv.dev === false) {
-    deprecate(
-      'depcheck',
-      'The option `dev` is deprecated. It leads a wrong result for missing dependencies'
-      + ' when it is `false`. This option will be removed and enforced to `true` in next'
-      + ' major version.',
-    );
-  }
-}
-
 export default function cli(args, log, error, exit) {
   const opt = yargs(args)
     .usage('Usage: $0 [DIRECTORY]')
@@ -92,7 +80,6 @@ export default function cli(args, log, error, exit) {
       'ignore-bin-package': false,
       'skip-missing': false,
     })
-    .describe('dev', '[DEPRECATED] Check on devDependecies')
     .describe('ignore-bin-package', 'Ignore package with bin entry')
     .describe('skip-missing', 'Skip calculation of missing dependencies')
     .describe('json', 'Output results to JSON')
@@ -104,8 +91,6 @@ export default function cli(args, log, error, exit) {
     .version('version', 'Show version number', version)
     .help('help', 'Show this help message');
 
-  checkDeprecation(opt.argv);
-
   const dir = opt.argv._[0] || '.';
   const rootDir = path.resolve(dir);
 
@@ -115,7 +100,6 @@ export default function cli(args, log, error, exit) {
       `Path ${dir} does not contain a package.json file`,
     ))
     .then(() => depcheck(rootDir, {
-      withoutDev: !opt.argv.dev,
       ignoreBinPackage: opt.argv.ignoreBinPackage,
       ignoreMatches: (opt.argv.ignores || '').split(','),
       ignoreDirs: (opt.argv.ignoreDirs || '').split(','),
diff --git a/src/constants.js b/src/constants.js
index a60b7ad7..5efb9f3b 100644
--- a/src/constants.js
+++ b/src/constants.js
@@ -19,7 +19,6 @@ export const availableDetectors = constructComponent(component, 'detector');
 export const availableSpecials = constructComponent(component, 'special');
 
 export const defaultOptions = {
-  withoutDev: false,
   ignoreBinPackage: false,
   ignoreMatches: [
   ],
diff --git a/src/index.js b/src/index.js
index 37c3b6a4..5b723903 100644
--- a/src/index.js
+++ b/src/index.js
@@ -40,7 +40,6 @@ export default function depcheck(rootDir, options, callback) {
   const getOption = (key) =>
     (lodash.isUndefined(options[key]) ? defaultOptions[key] : options[key]);
 
-  const withoutDev = getOption('withoutDev');
   const ignoreBinPackage = getOption('ignoreBinPackage');
   const ignoreMatches = getOption('ignoreMatches');
   const ignoreDirs = lodash.union(defaultOptions.ignoreDirs, options.ignoreDirs);
@@ -54,7 +53,7 @@ export default function depcheck(rootDir, options, callback) {
 
   const metadata = options.package || readJSON(path.join(rootDir, 'package.json'));
   const dependencies = metadata.dependencies || {};
-  const devDependencies = !withoutDev && metadata.devDependencies ? metadata.devDependencies : {};
+  const devDependencies = metadata.devDependencies ? metadata.devDependencies : {};
   const peerDeps = Object.keys(metadata.peerDependencies || {});
   const optionalDeps = Object.keys(metadata.optionalDependencies || {});
   const deps = filterDependencies(rootDir, ignoreBinPackage, ignoreMatches, dependencies);
diff --git a/test/cli.js b/test/cli.js
index 4d95bfaa..ff107895 100644
--- a/test/cli.js
+++ b/test/cli.js
@@ -14,10 +14,6 @@ function makeArgv(module, options) {
     argv.push('--json');
   }
 
-  if (options.withoutDev) {
-    argv.push('--dev=false');
-  }
-
   if (typeof options.ignoreBinPackage !== 'undefined') {
     argv.push(`--ignore-bin-package=${options.ignoreBinPackage}`);
   }
diff --git a/test/spec.js b/test/spec.js
index 5e830474..6b1186f7 100644
--- a/test/spec.js
+++ b/test/spec.js
@@ -6,7 +6,6 @@ export default [
     name: 'detect missing module for dynamic import() when missing in package.json',
     module: 'import_function_missing',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -23,7 +22,6 @@ export default [
     name: 'find module for dynamic import() when present',
     module: 'import_function',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -38,7 +36,6 @@ export default [
     name: 'find module for dynamic import() with magic Webpack comment',
     module: 'import_function_webpack',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -53,7 +50,6 @@ export default [
     name: 'missing module for require.resolve when missing in package.json',
     module: 'require_resolve_missing',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -70,7 +66,6 @@ export default [
     name: 'find module for require.resolve when present',
     module: 'require_resolve',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -85,7 +80,6 @@ export default [
     name: 'find unused dependencies',
     module: 'bad',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: ['optimist'],
@@ -125,7 +119,6 @@ export default [
     name: 'find all dependencies',
     module: 'good',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -143,7 +136,6 @@ export default [
     name: 'find all dependencies in ES6 files',
     module: 'good_es6',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: ['unsupported-syntax'],
@@ -171,7 +163,6 @@ export default [
     name: 'find all dependencies gatsby',
     module: 'gatsby',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: ['gatsby-plugin-react-helmet', 'gatsby-plugin-sass'],
@@ -185,7 +176,6 @@ export default [
     name: 'recognize experimental ES7 syntax enabled in Babel by default',
     module: 'good_es7',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -200,7 +190,6 @@ export default [
     name: 'support flow syntax in ES7 modules',
     module: 'good_es7_flow',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -319,7 +308,6 @@ export default [
     name: 'find grunt dependencies',
     module: 'grunt',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -334,7 +322,6 @@ export default [
     name: 'find grunt task dependencies',
     module: 'grunt-tasks',
     options: {
-      withoutDev: true,
     },
     expected: {
       dependencies: [],
@@ -349,7 +336,6 @@ export default [
     name: 'find unused package in devDependencies',
     module: 'dev',
     options: {
-      withoutDev: false,
     },
     expected: {
       dependencies: [],