diff --git a/include/__config b/include/__config
index 9da235efa..83e6e2a5d 100644
--- a/include/__config
+++ b/include/__config
@@ -719,10 +719,12 @@ template <unsigned> struct __static_assert_check {};
 #define _LIBCPP_LOCALE__L_EXTENSIONS 1
 #endif
 
-#if !defined(_WIN32) && !defined(__ANDROID__) && !defined(_NEWLIB_VERSION) && \
-    !defined(__CloudABI__)
+#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
+// Most unix variants have catopen.  These are the specific ones that don't.
+#if !defined(_WIN32) && !defined(__ANDROID__) && !defined(_NEWLIB_VERSION)
 #define _LIBCPP_HAS_CATOPEN 1
 #endif
+#endif
 
 #ifdef __FreeBSD__
 #define _DECLARE_C99_LDBL_MATH 1