diff --git a/libcxx/include/math.h b/libcxx/include/math.h
index c9b4733e9c446..194df2077bb1c 100644
--- a/libcxx/include/math.h
+++ b/libcxx/include/math.h
@@ -510,11 +510,7 @@ _LIBCPP_INLINE_VISIBILITY
 bool
 __libcpp_isnan(_A1 __lcpp_x) _NOEXCEPT
 {
-#if __has_builtin(__builtin_isnan)
-    return __builtin_isnan(__lcpp_x);
-#else
     return isnan(__lcpp_x);
-#endif
 }
 
 #undef isnan