diff --git a/index.js b/index.js
index b9df2d75b2d15cfbde214381e0063179434ee47e..6680b54d1532a8104e00be86c74ba1fa689ee379 100644
--- a/index.js
+++ b/index.js
@@ -32,7 +32,7 @@ export default function alphaSort(options = {}) {
 
 	if (options.caseInsensitive) {
 		return (left, right) =>
-			compareWith(left, right, value => value.toLowerCase()) ||
+			compareWith(left, right, value => value.toString().toLowerCase()) ||
 			compare(left, right);
 	}