diff --git a/config.h b/config.h
index 99915f4b..906fad48 100644
--- a/config.h
+++ b/config.h
@@ -9,8 +9,6 @@
 
 /* ============================================================
  * Compatibility defines
- *
- * Generally for Windows native support.
  * ============================================================ */
 #if defined(_MSC_VER) && _MSC_VER < 1900
 #  define snprintf sprintf_s
@@ -29,7 +27,11 @@
 #define uthash_malloc(sz) mosquitto__malloc(sz)
 #define uthash_free(ptr,sz) mosquitto__free(ptr)
 
-#define _DEFAULT_SOURCE 1
-#define _POSIX_C_SOURCE 200809L
+#ifdef __APPLE__
+#  define __DARWIN_C_SOURCE
+#else
+#  define _DEFAULT_SOURCE 1
+#  define _POSIX_C_SOURCE 200809L
+#endif
 
 #endif