diff --git a/source/blender/windowmanager/intern/wm_window.c b/source/blender/windowmanager/intern/wm_window.c
index 226f4f2aa60..be202a23d33 100644
--- a/source/blender/windowmanager/intern/wm_window.c
+++ b/source/blender/windowmanager/intern/wm_window.c
@@ -1129,7 +1129,8 @@ void WM_event_remove_timer(wmWindowManager *wm, wmWindow *UNUSED(win), wmTimer *
 			wmEvent *event;
 			for (event = win->queue.first; event; event = event->next) {
 				if (event->customdata == wt) {
-					//event->customdata = NULL;
+					event->customdata = NULL;
+					event->type = EVENT_NONE;	/* timer users customdata, dont want NULL == NULL */
 				}
 			}
 		}
diff --git a/source/blender/windowmanager/wm_event_types.h b/source/blender/windowmanager/wm_event_types.h
index de28cf5409d..c90bbaf8d6c 100644
--- a/source/blender/windowmanager/wm_event_types.h
+++ b/source/blender/windowmanager/wm_event_types.h
@@ -53,6 +53,8 @@
 #define MOUSEX		4
 #define MOUSEY		5
 
+/* non-event, for example disabled timer */
+#define EVENT_NONE		0
 /* MOUSE : 0x00x */
 #define LEFTMOUSE		1
 #define MIDDLEMOUSE		2