--- text2pcap.c
+++ text2pcap.c
@@ -77,6 +77,19 @@
  * snaplength is automatically set to 64K.
  */
 
+/*
+ * Just make sure we include the prototype for strptime as well
+ * (needed for glibc 2.2) but make sure we do this only if not
+ * yet defined.
+ */
+
+#ifndef __USE_XOPEN
+#  define __USE_XOPEN
+#endif
+#ifndef _XOPEN_SOURCE
+#  define _XOPEN_SOURCE
+#endif
+
 #ifdef HAVE_CONFIG_H
 # include "config.h"
 #endif
@@ -87,15 +100,6 @@
 #include <string.h>
 #include <wiretap/file_util.h>
 
-/*
- * Just make sure we include the prototype for strptime as well
- * (needed for glibc 2.2) but make sure we do this only if not
- * yet defined.
- */
-#ifndef __USE_XOPEN
-#  define __USE_XOPEN
-#endif
-
 #include <time.h>
 #include <glib.h>