diff --git a/include/layers.h b/include/layers.h
index 0eaccbb0..da88aafe 100644
--- a/include/layers.h
+++ b/include/layers.h
@@ -6,6 +6,8 @@
 
 struct server;
 
+#define LAB_NR_LAYERS (4)
+
 enum layer_parent {
 	LAYER_PARENT_LAYER,
 	LAYER_PARENT_POPUP,
@@ -29,6 +31,7 @@ struct lab_layer_surface {
 	struct server *server;
 };
 
+/* FIXME: do we still need lab_layer_popup and lab_layer_subsurface? */
 struct lab_layer_popup {
 	struct wlr_xdg_popup *wlr_popup;
 	enum layer_parent parent_type;
diff --git a/src/layers.c b/src/layers.c
index 94bf07ac..901a72ec 100644
--- a/src/layers.c
+++ b/src/layers.c
@@ -29,7 +29,7 @@ arrange_layers(struct output *output)
 			&full_area.width, &full_area.height);
 	struct wlr_box usable_area = full_area;
 
-	for (int i = 0; i < 4; i++) {
+	for (int i = 0; i < LAB_NR_LAYERS; i++) {
 		struct lab_layer_surface *lab_layer_surface;
 		wl_list_for_each(lab_layer_surface, &output->layers[i], link) {
 			struct wlr_scene_layer_surface_v1 *scene_layer_surface =
diff --git a/src/output.c b/src/output.c
index 1b29183d..07700c58 100644
--- a/src/output.c
+++ b/src/output.c
@@ -111,7 +111,7 @@ new_output_notify(struct wl_listener *listener, void *data)
 	output->frame.notify = output_frame_notify;
 	wl_signal_add(&wlr_output->events.frame, &output->frame);
 
-	for (int i = 0; i < 4; i++) {
+	for (int i = 0; i < LAB_NR_LAYERS; i++) {
 		wl_list_init(&output->layers[i]);
 		output->layer_tree[i] =
 			wlr_scene_tree_create(&server->scene->node);