diff --git a/tools/wpp/wpp.c b/tools/wpp/wpp.c
index d4b5465a71f..d2711a1d361 100644
--- a/tools/wpp/wpp.c
+++ b/tools/wpp/wpp.c
@@ -28,6 +28,8 @@
 #include "wpp_private.h"
 #include "wpp.h"
 
+int ppdebug;
+
 static void add_special_defines(void)
 {
     time_t now = time(NULL);