diff --git a/include/labwc.h b/include/labwc.h
index 7691c9d0..8f5aa989 100644
--- a/include/labwc.h
+++ b/include/labwc.h
@@ -188,13 +188,14 @@ struct server {
 	struct menu *menu_current;
 };
 
+#define LAB_NR_LAYERS (4)
 struct output {
 	struct wl_list link; /* server::outputs */
 	struct server *server;
 	struct wlr_output *wlr_output;
 	struct wlr_scene_output *scene_output;
-	struct wl_list layers[4];
-	struct wlr_scene_tree *layer_tree[4];
+	struct wl_list layers[LAB_NR_LAYERS];
+	struct wlr_scene_tree *layer_tree[LAB_NR_LAYERS];
 	struct wlr_box usable_area;
 
 	struct lab_data_buffer *osd_buffer;
@@ -202,6 +203,7 @@ struct output {
 	struct wl_listener destroy;
 	struct wl_listener frame;
 };
+#undef LAB_NR_LAYERS
 
 enum view_type {
 	LAB_XDG_SHELL_VIEW,
diff --git a/include/layers.h b/include/layers.h
index 033b89fd..f7d3f2b2 100644
--- a/include/layers.h
+++ b/include/layers.h
@@ -7,8 +7,6 @@
 struct server;
 struct output;
 
-#define LAB_NR_LAYERS (4)
-
 struct lab_layer_surface {
 	struct wl_list link; /* output::layers */
 	struct wlr_scene_layer_surface_v1 *scene_layer_surface;
diff --git a/src/layers.c b/src/layers.c
index 2cdba567..1d6b2b6d 100644
--- a/src/layers.c
+++ b/src/layers.c
@@ -34,7 +34,8 @@ layers_arrange(struct output *output)
 		return;
 	}
 
-	for (int i = 0; i < LAB_NR_LAYERS; i++) {
+	int nr_layers = sizeof(output->layers) / sizeof(output->layers[0]);
+	for (int i = 0; i < 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 215a2611..c9981af3 100644
--- a/src/output.c
+++ b/src/output.c
@@ -111,7 +111,8 @@ 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 < LAB_NR_LAYERS; i++) {
+	int nr_layers = sizeof(output->layers) / sizeof(output->layers[0]);
+	for (int i = 0; i < nr_layers; i++) {
 		wl_list_init(&output->layers[i]);
 		output->layer_tree[i] =
 			wlr_scene_tree_create(&server->scene->node);