diff --git a/buffer.c b/buffer.c
index 50908b19..94a30bc5 100644
--- a/buffer.c
+++ b/buffer.c
@@ -26,6 +26,7 @@
  */
 
 #include "event2/event-config.h"
+#include "event-private.h"
 
 #ifdef WIN32
 #include <winsock2.h>
@@ -34,8 +35,9 @@
 #endif
 
 #ifdef _EVENT_HAVE_VASPRINTF
-/* If we have vasprintf, we need to define this before we include stdio.h. */
-#define _GNU_SOURCE
+/* If we have vasprintf, we need to define _GNU_SOURCE before we include 
+ * stdio.h.  This comes from event-private.h.
+ */
 #endif
 
 #include <sys/types.h>
diff --git a/evutil.c b/evutil.c
index 2cb33370..5c2e8395 100644
--- a/evutil.c
+++ b/evutil.c
@@ -26,7 +26,7 @@
 
 #include "event2/event-config.h"
 
-#define _GNU_SOURCE
+#include "event-private.h"
 
 #ifdef WIN32
 #include <winsock2.h>