diff --git a/src/post_modules/GTK/configure.in b/src/post_modules/GTK/configure.in
index 3d06754ea5d0e630ba006801d960365b0bd387d3..a7a626d00fe17d7ac58f3326ba7c4337b375d5c8 100644
--- a/src/post_modules/GTK/configure.in
+++ b/src/post_modules/GTK/configure.in
@@ -122,6 +122,7 @@ dnl
       AC_TRY_RUN([
 #include <gtk/gtk.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 int
 main ()