diff --git a/src/bin/tetris/main.rs b/src/bin/tetris/main.rs
index 384c336..8c5d16f 100644
--- a/src/bin/tetris/main.rs
+++ b/src/bin/tetris/main.rs
@@ -91,7 +91,7 @@ impl GridPosition {
         let x = self.x as isize + other_x;
         let y = self.y as isize + other_y;
 
-        if x > X_MAX as isize {
+        if x >= X_MAX as isize {
             Err(GameError::OutOfBoundsLeft)
         } else if x < 0 {
             Err(GameError::OutOfBoundsRight)