Include config.h
diff --git a/gtp/gtp.c b/gtp/gtp.c
index d1b8cca..a6aebb9 100644
--- a/gtp/gtp.c
+++ b/gtp/gtp.c
@@ -48,6 +48,7 @@
 
 #include <stdint.h> /* ISO C99 types */
 
+#include "../config.h"
 #include "pdp.h"
 #include "gtp.h"
 #include "gtpie.h"