diff --git a/lodash.js b/lodash.js
index 4d800bb6e..1a8d099a2 100644
--- a/lodash.js
+++ b/lodash.js
@@ -1550,11 +1550,8 @@
     function isEqual(a, b, callback, thisArg, stackA, stackB) {
       // used to indicate that when comparing objects, `a` has at least the properties of `b`
       var whereIndicator = callback === indicatorObject;
-      if (callback && !whereIndicator) {
-        callback = (typeof thisArg == 'undefined')
-          ? callback
-          : lodash.createCallback(callback, thisArg, 2);
-
+      if (typeof callback == 'function' && !whereIndicator) {
+        callback = lodash.createCallback(callback, thisArg, 2);
         var result = callback(a, b);
         if (typeof result != 'undefined') {
           return !!result;
diff --git a/test/test.js b/test/test.js
index 3214eb544..44c707979 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1386,6 +1386,14 @@
         strictEqual(actual, false);
       });
     });
+
+    test('should ensure `callback` is a function', function() {
+      var array = [1, 2, 3],
+          eq = _.partial(_.isEqual, array),
+          actual = _.every([array, [1, 0, 3]], eq);
+
+      strictEqual(actual, false);
+    })
   }());
 
   /*--------------------------------------------------------------------------*/