diff --git a/panda/src/tform/mouseWatcher.h b/panda/src/tform/mouseWatcher.h
index 3bba14ed37..b3a1124a3b 100644
--- a/panda/src/tform/mouseWatcher.h
+++ b/panda/src/tform/mouseWatcher.h
@@ -34,6 +34,7 @@
 #include "bitArray.h"
 #include "clockObject.h"
 #include "pvector.h"
+#include "displayRegion.h"
 
 class MouseWatcherParameter;
 class DisplayRegion;