diff --git a/src/picom.c b/src/picom.c
index c66f940a70..1c20089641 100644
--- a/src/picom.c
+++ b/src/picom.c
@@ -1654,6 +1654,10 @@ static void handle_pending_updates(struct session *ps, double delta_t) {
 		ps->pending_updates = false;
 	}
 
+	if (ps->backend_data == NULL) {
+		return;
+	}
+
 	wm_stack_foreach_safe(ps->wm, cursor, tmp) {
 		auto w = wm_ref_deref(cursor);
 		BUG_ON(w != NULL && w->tree_ref != cursor);