diff --git a/.changeset/hot-yaks-flow.md b/.changeset/hot-yaks-flow.md
new file mode 100644
index 000000000..a6c9313f8
--- /dev/null
+++ b/.changeset/hot-yaks-flow.md
@@ -0,0 +1,5 @@
+---
+'@emotion/is-prop-valid': minor
+---
+
+Source code has been migrated to TypeScript. From now on type declarations will be emitted based on that, instead of being hand-written.
diff --git a/packages/is-prop-valid/package.json b/packages/is-prop-valid/package.json
index 03f0b6d55..148782dfa 100644
--- a/packages/is-prop-valid/package.json
+++ b/packages/is-prop-valid/package.json
@@ -4,7 +4,7 @@
   "description": "A function to check whether a prop is valid for HTML and SVG elements",
   "main": "dist/emotion-is-prop-valid.cjs.js",
   "module": "dist/emotion-is-prop-valid.esm.js",
-  "types": "types/index.d.ts",
+  "types": "dist/emotion-is-prop-valid.cjs.d.ts",
   "license": "MIT",
   "repository": "https://github.com/emotion-js/emotion/tree/main/packages/is-prop-valid",
   "scripts": {
@@ -21,8 +21,7 @@
   },
   "files": [
     "src",
-    "dist",
-    "types/*.d.ts"
+    "dist"
   ],
   "browser": {
     "./dist/emotion-is-prop-valid.cjs.js": "./dist/emotion-is-prop-valid.browser.cjs.js",
diff --git a/packages/is-prop-valid/src/index.js b/packages/is-prop-valid/src/index.ts
similarity index 76%
rename from packages/is-prop-valid/src/index.js
rename to packages/is-prop-valid/src/index.ts
index 2e847785b..88fb41532 100644
--- a/packages/is-prop-valid/src/index.js
+++ b/packages/is-prop-valid/src/index.ts
@@ -1,11 +1,9 @@
 import memoize from '@emotion/memoize'
 
-/*
-declare var codegen: { require: string => RegExp }
-*/
+declare const codegen: { require: (path: string) => any }
 
 // eslint-disable-next-line no-undef
-const reactPropsRegex = codegen.require('./props')
+const reactPropsRegex: RegExp = codegen.require('./props')
 
 // https://esbench.com/bench/5bfee68a4cd7e6009ef61d23
 const isPropValid = /* #__PURE__ */ memoize(
diff --git a/packages/is-prop-valid/src/props.js b/packages/is-prop-valid/src/props.js
index 873fa118d..326d7898b 100644
--- a/packages/is-prop-valid/src/props.js
+++ b/packages/is-prop-valid/src/props.js
@@ -1,3 +1,6 @@
+/**
+ * This module needs to remain pure JavaScript for codegen to work on it
+ */
 const props = {
   // react props
   // https://github.com/facebook/react/blob/5495a7f24aef85ba6937truetrue1ce962673ca9f5fde6/src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
diff --git a/packages/is-prop-valid/types/index.d.ts b/packages/is-prop-valid/types/index.d.ts
index 2ca137567..ad44a5b20 100644
--- a/packages/is-prop-valid/types/index.d.ts
+++ b/packages/is-prop-valid/types/index.d.ts
@@ -1,5 +1,3 @@
-// Definitions by: Junyoung Clare Jang <https://github.com/Ailrun>
 // TypeScript Version: 2.1
 
-declare function isPropValid(string: PropertyKey): boolean
-export default isPropValid
+export { default } from '../src'
diff --git a/packages/is-prop-valid/types/tslint.json b/packages/is-prop-valid/types/tslint.json
index 0f215d5ec..ac5485b6c 100644
--- a/packages/is-prop-valid/types/tslint.json
+++ b/packages/is-prop-valid/types/tslint.json
@@ -17,6 +17,7 @@
       "check-preblock"
     ],
 
-    "no-unnecessary-generics": false
+    "no-unnecessary-generics": false,
+    "no-default-import": false
   }
 }
diff --git a/packages/memoize/types/tests.ts b/packages/memoize/types/tests.ts
index 1615284e1..81b32b8ba 100644
--- a/packages/memoize/types/tests.ts
+++ b/packages/memoize/types/tests.ts
@@ -1,4 +1,4 @@
-import memoize from '../src'
+import memoize from '@emotion/memoize'
 
 // $ExpectType string[]
 memoize((arg: string) => [arg])('foo')
diff --git a/packages/weak-memoize/types/tests.ts b/packages/weak-memoize/types/tests.ts
index 9d54d2849..8daa3243d 100644
--- a/packages/weak-memoize/types/tests.ts
+++ b/packages/weak-memoize/types/tests.ts
@@ -1,4 +1,4 @@
-import weakMemoize from '../src'
+import weakMemoize from '@emotion/weak-memoize'
 
 interface Foo {
   bar: 'xyz'