diff --git a/packages/tailwindcss-class-names/src/index.js b/packages/tailwindcss-class-names/src/index.js
index 06f1b8a..f9f39c4 100644
--- a/packages/tailwindcss-class-names/src/index.js
+++ b/packages/tailwindcss-class-names/src/index.js
@@ -32,7 +32,10 @@ function glob(pattern, options = {}) {
 }
 
 function arraysEqual(arr1, arr2) {
-  return JSON.stringify(arr1.sort()) === JSON.stringify(arr2.sort())
+  return (
+    JSON.stringify(arr1.concat([]).sort()) ===
+    JSON.stringify(arr2.concat([]).sort())
+  )
 }
 
 export default async function getClassNames(