diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -348,7 +348,8 @@
 //      Use rand_s(), for use on Windows.
 //      When this option is used, the token passed to `std::random_device`'s
 //      constructor *must* be "/dev/urandom" -- anything else is an error.
-#if defined(__OpenBSD__) || defined(__APPLE__)
+#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__) || \
+    defined(__OpenBSD__) || defined(__DragonFly__)
 #  define _LIBCPP_USING_ARC4_RANDOM
 #elif defined(__wasi__)
 #  define _LIBCPP_USING_GETENTROPY