diff --git a/include/sway/tree/container.h b/include/sway/tree/container.h
index 7e78cbef..728daa84 100644
--- a/include/sway/tree/container.h
+++ b/include/sway/tree/container.h
@@ -295,6 +295,6 @@ bool container_is_floating(struct sway_container *container);
 /**
  * Get a container's box in layout coordinates.
  */
-struct wlr_box *container_get_box(struct sway_container *container);
+void container_get_box(struct sway_container *container, struct wlr_box *box);
 
 #endif
diff --git a/sway/tree/container.c b/sway/tree/container.c
index 8446c457..ab3d9dbd 100644
--- a/sway/tree/container.c
+++ b/sway/tree/container.c
@@ -988,11 +988,9 @@ bool container_is_floating(struct sway_container *container) {
 	return container->parent == workspace->sway_workspace->floating;
 }
 
-struct wlr_box *container_get_box(struct sway_container *container) {
-	struct wlr_box *box = calloc(1, sizeof(struct wlr_box));
+void container_get_box(struct sway_container *container, struct wlr_box *box) {
 	box->x = container->x;
 	box->y = container->y;
 	box->width = container->width;
 	box->height = container->height;
-	return box;
 }