diff --git a/src/ng/directive/ngClass.js b/src/ng/directive/ngClass.js
index 664e4810ce21..fc7b6db2c032 100644
--- a/src/ng/directive/ngClass.js
+++ b/src/ng/directive/ngClass.js
@@ -125,6 +125,8 @@ function classDirective(name, selector) {
   }
 
   function toClassString(classValue) {
+    if (!classValue) return classValue;
+
     var classString = classValue;
 
     if (isArray(classValue)) {
@@ -133,6 +135,8 @@ function classDirective(name, selector) {
       classString = Object.keys(classValue).
         filter(function(key) { return classValue[key]; }).
         join(' ');
+    } else if (!isString(classValue)) {
+      classString = classValue + '';
     }
 
     return classString;
diff --git a/test/ng/directive/ngClassSpec.js b/test/ng/directive/ngClassSpec.js
index 0180d67a6aa4..74500505fd84 100644
--- a/test/ng/directive/ngClassSpec.js
+++ b/test/ng/directive/ngClassSpec.js
@@ -88,6 +88,12 @@ describe('ngClass', function() {
     expect(element.hasClass('AnotB')).toBeFalsy();
   }));
 
+  it('should not break when passed non-string/array/object, truthy values', inject(function($rootScope, $compile) {
+    element = $compile('<div ng-class="42"></div>')($rootScope);
+    $rootScope.$digest();
+    expect(element.hasClass('42')).toBeTruthy();
+  }));
+
   it('should support adding multiple classes via an array mixed with conditionally via a map', inject(function($rootScope, $compile) {
     element = $compile('<div class="existing" ng-class="[\'A\', {\'B\': condition}]"></div>')($rootScope);
     $rootScope.$digest();