diff --git a/xmdev/src/main.c b/xmdev/src/main.c
index acb261c..4b568c7 100644
--- a/xmdev/src/main.c
+++ b/xmdev/src/main.c
@@ -1,4 +1,4 @@
-#define _XOPEN_SOURCE
+#define _XOPEN_SOURCE 700
 #include <Xm/Xm.h>
 #include <Xm/Form.h>
 #include <Xm/PushB.h>