diff --git a/include/cmath b/include/cmath
index ec28e0e45..608b9151f 100644
--- a/include/cmath
+++ b/include/cmath
@@ -541,19 +541,19 @@ inline _LIBCPP_INLINE_VISIBILITY long double hypot( long double x, long double y
 
 template <class _A1, class _A2, class _A3>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::__lazy_enable_if
+typename __lazy_enable_if
 <
-    std::is_arithmetic<_A1>::value &&
-    std::is_arithmetic<_A2>::value &&
-    std::is_arithmetic<_A3>::value,
-    std::__promote<_A1, _A2, _A3>
+    is_arithmetic<_A1>::value &&
+    is_arithmetic<_A2>::value &&
+    is_arithmetic<_A3>::value,
+    __promote<_A1, _A2, _A3>
 >::type
 hypot(_A1 __lcpp_x, _A2 __lcpp_y, _A3 __lcpp_z) _NOEXCEPT
 {
-    typedef typename std::__promote<_A1, _A2, _A3>::type __result_type;
-    static_assert((!(std::is_same<_A1, __result_type>::value &&
-                     std::is_same<_A2, __result_type>::value &&
-                     std::is_same<_A3, __result_type>::value)), "");
+    typedef typename __promote<_A1, _A2, _A3>::type __result_type;
+    static_assert((!(is_same<_A1, __result_type>::value &&
+                     is_same<_A2, __result_type>::value &&
+                     is_same<_A3, __result_type>::value)), "");
     return hypot((__result_type)__lcpp_x, (__result_type)__lcpp_y, (__result_type)__lcpp_z);
 }
 #endif