diff --git a/sway/desktop/fx_renderer.c b/sway/desktop/fx_renderer.c
index 7c8ebc43..6810fa26 100644
--- a/sway/desktop/fx_renderer.c
+++ b/sway/desktop/fx_renderer.c
@@ -361,7 +361,7 @@ void fx_render_rect(struct fx_renderer *renderer, const struct wlr_box *box,
 void fx_render_border_corner(struct fx_renderer *renderer, const struct wlr_box *box,
 		const float color[static 4], const float projection[static 9],
 		enum corner_location corner_location, int radius, int border_thickness) {
-	if (box->width == 0 || box->height == 0) {
+	if (border_thickness == 0 || box->width == 0 || box->height == 0) {
 		return;
 	}
 	assert(box->width > 0 && box->height > 0);