diff --git a/backend/multi/backend.c b/backend/multi/backend.c
index 94b7dd60..9afca47d 100644
--- a/backend/multi/backend.c
+++ b/backend/multi/backend.c
@@ -112,7 +112,7 @@ static void output_remove_reemit(struct wl_listener *listener, void *data) {
 
 void wlr_multi_backend_add(struct wlr_backend *_multi,
 		struct wlr_backend *backend) {
-	assert(wlr_backend_is_multi(backend));
+	assert(wlr_backend_is_multi(_multi));
 
 	struct wlr_multi_backend *multi = (struct wlr_multi_backend *)_multi;
 	struct subbackend_state *sub = calloc(1, sizeof(struct subbackend_state));
diff --git a/types/wlr_output.c b/types/wlr_output.c
index 04dcbfa5..b4618194 100644
--- a/types/wlr_output.c
+++ b/types/wlr_output.c
@@ -178,13 +178,16 @@ void wlr_output_destroy(struct wlr_output *output) {
 	wlr_texture_destroy(output->cursor.texture);
 	wlr_renderer_destroy(output->cursor.renderer);
 
-	output->impl->destroy(output);
 	for (size_t i = 0; output->modes && i < output->modes->length; ++i) {
 		struct wlr_output_mode *mode = output->modes->items[i];
 		free(mode);
-		free(mode);
 	}
 	list_free(output->modes);
+	if (output->impl->destroy) {
+		output->impl->destroy(output);
+	} else {
+		free(output);
+	}
 }
 
 void wlr_output_effective_resolution(struct wlr_output *output,