diff --git a/render/mask.h b/render/mask.h
index 90a622b3..2d507a63 100644
--- a/render/mask.h
+++ b/render/mask.h
@@ -2,6 +2,7 @@
 #define __mask_h
 
 #include <X11/Xlib.h>
+#include <glib.h>
 
 typedef struct {
   Pixmap mask;