Solution to angular#1911

Here is the solution to issue angular#1911

Author: raftalks

src/ng/directive/input.js

@@ -643,7 +643,7 @@ function checkboxInputType(scope, element, attr, ctrl) {
   };
 
   ctrl.$formatters.push(function(value) {
-    return value === trueValue;
+    return value == trueValue;
   });
 
   ctrl.$parsers.push(function(value) {