diff --git a/.prettierignore b/.prettierignore
new file mode 100644
index 00000000..3e6dde73
--- /dev/null
+++ b/.prettierignore
@@ -0,0 +1,2 @@
+index.cjs.js
+index.umd.js
diff --git a/package.json b/package.json
index 3bc55b16..3eeee5e9 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
     "prettier:fix": "npm run prettier -- --write",
     "prettier": "prettier \"**/*.{js,json,md}\"",
     "regenerate": "node --experimental-modules regenerate.js && npm run prettier:fix",
-    "test": "node --experimental-modules index.test.js"
+    "test": "npm run prettier:check && node --experimental-modules index.test.js"
   },
   "repository": {
     "type": "git",
diff --git a/regenerate.js b/regenerate.js
index f2c16956..fcfbdebf 100644
--- a/regenerate.js
+++ b/regenerate.js
@@ -13,6 +13,7 @@ const ignoredFiles = [
   ".all-contributorsrc",
   ".gitignore",
   ".npmignore",
+  ".prettierignore",
   "index.cjs.js",
   "index.js",
   "index.test.js",