diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index d533dc0ef09..ea700d1ed97 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -674,6 +674,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public __bool_constant<__is_member_object_pointer(_Tp)>
     { };
 #else
+  template<typename _Tp>
+    struct is_function;
+
   template<typename>
     struct __is_member_object_pointer_helper
     : public false_type { };
@@ -696,6 +699,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public __bool_constant<__is_member_function_pointer(_Tp)>
     { };
 #else
+  template<typename _Tp>
+    struct is_function;
+
   template<typename>
     struct __is_member_function_pointer_helper
     : public false_type { };