diff --git a/packages/ckeditor5-admonition/package.json b/packages/ckeditor5-admonition/package.json
index 2d84b2145..e25a35048 100644
--- a/packages/ckeditor5-admonition/package.json
+++ b/packages/ckeditor5-admonition/package.json
@@ -11,6 +11,7 @@
     "ckeditor5-package-generator"
   ],
   "type": "module",
+  "source": "src/index.ts",
   "main": "dist/index.ts",
   "module": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/packages/ckeditor5-footnotes/package.json b/packages/ckeditor5-footnotes/package.json
index 0755f8c30..e22ff6979 100644
--- a/packages/ckeditor5-footnotes/package.json
+++ b/packages/ckeditor5-footnotes/package.json
@@ -11,6 +11,7 @@
     "ckeditor5-package-generator"
   ],
   "type": "module",
+  "source": "src/index.ts",
   "main": "dist/index.ts",
   "module": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/packages/ckeditor5-keyboard-marker/package.json b/packages/ckeditor5-keyboard-marker/package.json
index 5024f813e..4b0d2676e 100644
--- a/packages/ckeditor5-keyboard-marker/package.json
+++ b/packages/ckeditor5-keyboard-marker/package.json
@@ -11,6 +11,7 @@
     "ckeditor5-package-generator"
   ],
   "type": "module",
+  "source": "src/index.ts",
   "main": "dist/index.ts",
   "module": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/packages/ckeditor5-math/package.json b/packages/ckeditor5-math/package.json
index 7c58f2c78..5e9f639a6 100644
--- a/packages/ckeditor5-math/package.json
+++ b/packages/ckeditor5-math/package.json
@@ -12,6 +12,7 @@
     "katex"
   ],
   "type": "module",
+  "source": "src/index.ts",
   "main": "dist/index.ts",
   "module": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/packages/ckeditor5/package.json b/packages/ckeditor5/package.json
index 49562a8cc..c0133f506 100644
--- a/packages/ckeditor5/package.json
+++ b/packages/ckeditor5/package.json
@@ -4,6 +4,7 @@
   "version": "45.0.0",
   "private": true,
   "type": "module",
+  "source": "./src/index.ts",
   "main": "./dist/index.js",
   "module": "./dist/index.js",
   "types": "./dist/index.d.ts",
diff --git a/packages/highlightjs/package.json b/packages/highlightjs/package.json
index c6eb24ed1..76f3ba344 100644
--- a/packages/highlightjs/package.json
+++ b/packages/highlightjs/package.json
@@ -3,6 +3,7 @@
   "version": "0.0.1",
   "private": true,
   "type": "module",
+  "source": "./src/index.ts",
   "main": "./dist/index.js",
   "module": "./dist/index.js",
   "types": "./dist/index.d.ts",