diff --git a/backend/headless/output.c b/backend/headless/output.c
index 3cb35dcef..d200aa581 100644
--- a/backend/headless/output.c
+++ b/backend/headless/output.c
@@ -128,8 +128,8 @@ struct wlr_output *wlr_headless_add_output(struct wlr_backend *wlr_backend,
 	output_set_custom_mode(wlr_output, width, height, 0);
 	strncpy(wlr_output->make, "headless", sizeof(wlr_output->make));
 	strncpy(wlr_output->model, "headless", sizeof(wlr_output->model));
-	snprintf(wlr_output->name, sizeof(wlr_output->name), "HEADLESS-%d",
-		wl_list_length(&backend->outputs) + 1);
+	snprintf(wlr_output->name, sizeof(wlr_output->name), "HEADLESS-%ld",
+		++backend->last_output_num);
 
 	if (!wlr_egl_make_current(&output->backend->egl, output->egl_surface,
 			NULL)) {
diff --git a/include/backend/headless.h b/include/backend/headless.h
index 35280862d..66448071e 100644
--- a/include/backend/headless.h
+++ b/include/backend/headless.h
@@ -12,6 +12,7 @@ struct wlr_headless_backend {
 	struct wlr_renderer *renderer;
 	struct wl_display *display;
 	struct wl_list outputs;
+	size_t last_output_num;
 	struct wl_list input_devices;
 	struct wl_listener display_destroy;
 	bool started;