diff --git a/lodash.js b/lodash.js
index bd9a0f2f9..ab41fba39 100644
--- a/lodash.js
+++ b/lodash.js
@@ -5291,8 +5291,8 @@
         (WeakMap && getTag(new WeakMap) != weakMapTag)) {
       getTag = function(value) {
         var result = objectToString.call(value),
-            Ctor = result == objectTag ? value.constructor : null,
-            ctorString = toSource(Ctor);
+            Ctor = result == objectTag ? value.constructor : undefined,
+            ctorString = Ctor ? toSource(Ctor) : undefined;
 
         if (ctorString) {
           switch (ctorString) {
@@ -5791,12 +5791,15 @@
      * @returns {string} Returns the source code.
      */
     function toSource(func) {
-      if (isFunction(func)) {
+      if (func != null) {
         try {
           return funcToString.call(func);
         } catch (e) {}
+        try {
+          return (func + '');
+        } catch (e) {}
       }
-      return toString(func);
+      return '';
     }
 
     /**