diff --git a/src/jquery.validity.core.js b/src/jquery.validity.core.js
index 1fee51f..574cf11 100644
--- a/src/jquery.validity.core.js
+++ b/src/jquery.validity.core.js
@@ -1091,7 +1091,7 @@ function infer(field) {
         ret = arr.join(" ");
     }
 
-    return $.trim(ret);
+    return String.prototype.trim(ret);
 }
 
 // Capitalize the first character of the string argument.