diff --git a/mozilla/widget/src/xlib/nsAppShell.cpp b/mozilla/widget/src/xlib/nsAppShell.cpp
index 52eca0a0988..5c7f75c189e 100644
--- a/mozilla/widget/src/xlib/nsAppShell.cpp
+++ b/mozilla/widget/src/xlib/nsAppShell.cpp
@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <sys/time.h>
 #include <unistd.h>
+#include <ctype.h>
 #include <errno.h>
 
 #include "nsWidget.h"