diff --git a/lib/6to5/polyfill.js b/lib/6to5/polyfill.js
index 9c2cf47317..f6253cf6e9 100644
--- a/lib/6to5/polyfill.js
+++ b/lib/6to5/polyfill.js
@@ -34,8 +34,6 @@ require("./transformation/transformers/es6-generators/runtime");
 
 ensureSymbol("species");
 
-String.prototype.includes = String.prototype.includes || String.prototype.contains;
-
 // Abstract references
 
 ensureSymbol("referenceGet");