diff --git a/tools/wpp/wpp.c b/tools/wpp/wpp.c
index dd07480e034..7ceee3f3463 100644
--- a/tools/wpp/wpp.c
+++ b/tools/wpp/wpp.c
@@ -20,6 +20,7 @@
  */
 
 #include <time.h>
+#include <stdlib.h>
 
 #include "wpp_private.h"
 #include "wpp.h"