diff --git a/src/lib.rs b/src/lib.rs
index 49f12e9..9cb329e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -193,6 +193,7 @@ impl State {
         State { lvl }
     }
 
+    #[inline(always)]
     fn toggle_box(&mut self, pos: &Pos) {
         self.lvl[*pos] = if self.lvl[*pos] == Cell::Goal(true) {
             Cell::Goal(false)