diff --git a/Eigen/src/Core/util/XprHelper.h b/Eigen/src/Core/util/XprHelper.h
index 1217404d6..9ffb0474b 100644
--- a/Eigen/src/Core/util/XprHelper.h
+++ b/Eigen/src/Core/util/XprHelper.h
@@ -39,10 +39,12 @@ template<typename T> struct is_valid_index_type
 {
   enum { value =
 #if EIGEN_HAS_TYPE_TRAITS
-   internal::is_integral<T>::value || std::is_enum<T>::value
+    internal::is_integral<T>::value || std::is_enum<T>::value
+#else if EIGEN_COMP_MSVC >= 1500
+    internal::is_integral<T>::value || __is_enum(T)
 #else
-  // without C++11, we use is_convertible to Index instead of is_integral in order to treat enums as Index.
-  internal::is_convertible<T,Index>::value
+    // without C++11, we use is_convertible to Index instead of is_integral in order to treat enums as Index.
+    internal::is_convertible<T,Index>::value
 #endif
   };
 };