diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -333,7 +333,7 @@
 #  define _LIBCPP_SHORT_WCHAR   1
 #endif
 
-#if defined(__OpenBSD__)
+#if defined(__OpenBSD__) || defined(__APPLE__)
    // Certain architectures provide arc4random(). Prefer using
    // arc4random() over /dev/{u,}random to make it possible to obtain
    // random data even when using sandboxing mechanisms such as chroots,