diff --git a/packages/babel-preset-gatsby-package/.gitignore b/packages/babel-preset-gatsby-package/.gitignore
deleted file mode 100644
index 1d6fb326da1b3..0000000000000
--- a/packages/babel-preset-gatsby-package/.gitignore
+++ /dev/null
@@ -1,2 +0,0 @@
-yarn.lock
-dist/
diff --git a/packages/babel-preset-gatsby-package/__tests__/__snapshots__/index.js.snap b/packages/babel-preset-gatsby-package/lib/__tests__/__snapshots__/index.js.snap
similarity index 100%
rename from packages/babel-preset-gatsby-package/__tests__/__snapshots__/index.js.snap
rename to packages/babel-preset-gatsby-package/lib/__tests__/__snapshots__/index.js.snap
diff --git a/packages/babel-preset-gatsby-package/__tests__/babel-transform-compiler-flags.js b/packages/babel-preset-gatsby-package/lib/__tests__/babel-transform-compiler-flags.js
similarity index 100%
rename from packages/babel-preset-gatsby-package/__tests__/babel-transform-compiler-flags.js
rename to packages/babel-preset-gatsby-package/lib/__tests__/babel-transform-compiler-flags.js
diff --git a/packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/default/input.js b/packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/default/input.js
similarity index 100%
rename from packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/default/input.js
rename to packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/default/input.js
diff --git a/packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/default/output.mjs b/packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/default/output.mjs
similarity index 100%
rename from packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/default/output.mjs
rename to packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/default/output.mjs
diff --git a/packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/unused/input.js b/packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/unused/input.js
similarity index 100%
rename from packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/unused/input.js
rename to packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/unused/input.js
diff --git a/packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/unused/options.json b/packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/unused/options.json
similarity index 100%
rename from packages/babel-preset-gatsby-package/__tests__/fixtures/compiler-flags/unused/options.json
rename to packages/babel-preset-gatsby-package/lib/__tests__/fixtures/compiler-flags/unused/options.json
diff --git a/packages/babel-preset-gatsby-package/__tests__/fixtures/options.js b/packages/babel-preset-gatsby-package/lib/__tests__/fixtures/options.js
similarity index 75%
rename from packages/babel-preset-gatsby-package/__tests__/fixtures/options.js
rename to packages/babel-preset-gatsby-package/lib/__tests__/fixtures/options.js
index b4f1a1f9d6265..b6c2571923d7c 100644
--- a/packages/babel-preset-gatsby-package/__tests__/fixtures/options.js
+++ b/packages/babel-preset-gatsby-package/lib/__tests__/fixtures/options.js
@@ -3,7 +3,7 @@ const path = require("path")
 module.exports = {
   sourceType: "module",
   plugins: [
-    [path.resolve(__dirname, "../../src/babel-transform-compiler-flags.ts"),
+    [path.resolve(__dirname, "../../babel-transform-compiler-flags.js"),
       {
         availableFlags: ['MAJOR'],
         flags: {
diff --git a/packages/babel-preset-gatsby-package/__tests__/index.js b/packages/babel-preset-gatsby-package/lib/__tests__/index.js
similarity index 94%
rename from packages/babel-preset-gatsby-package/__tests__/index.js
rename to packages/babel-preset-gatsby-package/lib/__tests__/index.js
index 6c77f2693e33f..6b959547c91fc 100644
--- a/packages/babel-preset-gatsby-package/__tests__/index.js
+++ b/packages/babel-preset-gatsby-package/lib/__tests__/index.js
@@ -1,6 +1,6 @@
-const preset = require(`../src/index.js`)
+const preset = require(`../index.js`)
 
-jest.mock(`../src/resolver`, () => jest.fn(moduleName => moduleName))
+jest.mock(`../resolver`, () => jest.fn(moduleName => moduleName))
 
 
 describe(`babel-preset-gatsby-package`, () => {
diff --git a/packages/babel-preset-gatsby-package/lib/babel-transform-compiler-flags.js b/packages/babel-preset-gatsby-package/lib/babel-transform-compiler-flags.js
new file mode 100644
index 0000000000000..d229b2c22931e
--- /dev/null
+++ b/packages/babel-preset-gatsby-package/lib/babel-transform-compiler-flags.js
@@ -0,0 +1,71 @@
+
+/**
+ * @typedef {import('@babel/core').NodePath} NodePath
+ * @typedef {import('@babel/core').PluginObj} PluginObj
+ * @typedef {import('@babel/core').PluginPass} PluginPass
+ * @typedef {import('@babel/core').types} BabelTypes
+ * @typedef {import('@babel/core').types.Identifier} Identifier
+ * @typedef {import('@babel/core').types.MemberExpression} MemberExpression
+ */
+
+/**
+ * @typedef {Object} IPluginOptions
+ * @property {Record<string, string>} flags
+ * @property {Array<string>} availableFlags
+ */
+
+/**
+ *
+ * @param {{ types: BabelTypes }} args
+ * @param {Partial<IPluginOptions>} opts
+ * @returns {PluginObj}
+ */
+module.exports = function compilerFlags(
+  {
+    types: t,
+  },
+  opts
+) {
+  if (!opts.flags) {
+    throw new Error(`flags option needs to be set`)
+  }
+  if (!opts.availableFlags) {
+    throw new Error(`availableFlags option needs to be set`)
+  }
+
+  return {
+    name: `babel-transform-compiler-flags`,
+    visitor: {
+      /**
+       * @param {NodePath} nodePath
+       * @param {PluginPass} state
+       */
+      Identifier(
+        nodePath,
+        state
+      ) {
+        const identifier = /** @type {Identifier} */ (nodePath.node)
+        const flags = /** @type {IPluginOptions} */ (state.opts).flags
+        const availableFlags = /** @type {IPluginOptions} */ (state.opts).availableFlags
+
+        if (
+          identifier.name === `_CFLAGS_` &&
+          t.isMemberExpression(nodePath.parent)
+        ) {
+          const parentNode = /** @type {MemberExpression} */ (nodePath.parent)
+          const cFlag = /** @type {Identifier} */ (parentNode.property).name
+
+          if (!availableFlags.includes(cFlag)) {
+            throw new Error(
+              `${cFlag} is not part of the available compiler flags.`
+            )
+          }
+
+          nodePath.parentPath.replaceWith(
+            t.stringLiteral(flags[cFlag] ? flags[cFlag] : ``)
+          )
+        }
+      },
+    },
+  }
+}
diff --git a/packages/babel-preset-gatsby-package/src/index.js b/packages/babel-preset-gatsby-package/lib/index.js
similarity index 100%
rename from packages/babel-preset-gatsby-package/src/index.js
rename to packages/babel-preset-gatsby-package/lib/index.js
diff --git a/packages/babel-preset-gatsby-package/src/resolver.js b/packages/babel-preset-gatsby-package/lib/resolver.js
similarity index 100%
rename from packages/babel-preset-gatsby-package/src/resolver.js
rename to packages/babel-preset-gatsby-package/lib/resolver.js
diff --git a/packages/babel-preset-gatsby-package/package.json b/packages/babel-preset-gatsby-package/package.json
index cd8508fc15c47..65234f6c851c5 100644
--- a/packages/babel-preset-gatsby-package/package.json
+++ b/packages/babel-preset-gatsby-package/package.json
@@ -31,12 +31,15 @@
     "@babel/core": "^7.11.6"
   },
   "license": "MIT",
-  "main": "dist/index.js",
+  "main": "lib/index.js",
   "engines": {
     "node": ">=12.13.0"
   },
+  "files": [
+    "lib/*.js"
+  ],
   "scripts": {
-    "build": "babel src --out-dir dist/ --ignore \"**/__tests__\" --ignore \"**/__mocks__\" --extensions \".ts,.js\"",
+    "build": "",
     "prepare": "cross-env NODE_ENV=production npm run build",
     "watch": "babel -w src --out-dir dist/ --ignore \"**/__tests__\" --extensions \".ts,.js\""
   }
diff --git a/packages/babel-preset-gatsby-package/src/babel-transform-compiler-flags.ts b/packages/babel-preset-gatsby-package/src/babel-transform-compiler-flags.ts
deleted file mode 100644
index 67a4938d792cf..0000000000000
--- a/packages/babel-preset-gatsby-package/src/babel-transform-compiler-flags.ts
+++ /dev/null
@@ -1,52 +0,0 @@
-import type { NodePath, PluginObj, types, PluginPass } from "@babel/core"
-
-interface IPluginOptions {
-  flags: Record<string, string>
-  availableFlags: Array<string>
-}
-
-export default function compilerFlags(
-  {
-    types: t,
-  }: {
-    types: typeof types
-  },
-  opts: Partial<IPluginOptions>
-): PluginObj {
-  if (!opts.flags) {
-    throw new Error(`flags option needs to be set`)
-  }
-  if (!opts.availableFlags) {
-    throw new Error(`availableFlags option needs to be set`)
-  }
-
-  return {
-    name: `babel-transform-compiler-flags`,
-    visitor: {
-      Identifier(
-        nodePath: NodePath<types.Identifier>,
-        state: PluginPass
-      ): void {
-        const flags = (state.opts as IPluginOptions).flags
-        const availableFlags = (state.opts as IPluginOptions).availableFlags
-
-        if (
-          nodePath.node.name === `_CFLAGS_` &&
-          t.isMemberExpression(nodePath.parent)
-        ) {
-          const cFlag = (nodePath.parent.property as types.Identifier).name
-
-          if (!availableFlags.includes(cFlag)) {
-            throw new Error(
-              `${cFlag} is not part of the available compiler flags.`
-            )
-          }
-
-          nodePath.parentPath.replaceWith(
-            t.stringLiteral(flags[cFlag] ? flags[cFlag] : ``)
-          )
-        }
-      },
-    },
-  }
-}
diff --git a/packages/babel-preset-gatsby-package/tsconfig.json b/packages/babel-preset-gatsby-package/tsconfig.json
index 7af82cd9557aa..1c6c8da61b49a 100644
--- a/packages/babel-preset-gatsby-package/tsconfig.json
+++ b/packages/babel-preset-gatsby-package/tsconfig.json
@@ -1,4 +1,8 @@
 {
   "extends": "../../tsconfig.json",
-  "strict": true
+  "strict": true,
+  "compilerOptions": {
+    "allowJs": true,
+    "checkJs": true
+  }
 }