diff --git a/ssl/ssltest.c b/ssl/ssltest.c
index 9ef43dfa8..79735126f 100644
--- a/ssl/ssltest.c
+++ b/ssl/ssltest.c
@@ -143,6 +143,9 @@
 #define _BSD_SOURCE 1		/* Or gethostname won't be declared properly
 				   on Linux and GNU platforms. */
 
+#define _XOPEN_SOURCE 500	/* Or isascii won't be declared properly on
+				   VMS (at least with DECompHP C).  */
+
 #include <assert.h>
 #include <errno.h>
 #include <limits.h>
@@ -154,8 +157,6 @@
 #define USE_SOCKETS
 #include "e_os.h"
 
-#define _XOPEN_SOURCE 500	/* Or isascii won't be declared properly on
-				   VMS (at least with DECompHP C).  */
 #include <ctype.h>
 
 #include <openssl/bio.h>