diff --git a/src/killer_sokoban/AbstractField.java b/src/killer_sokoban/AbstractField.java
index 56d8a69f4098f84ca8c9e586b918803ec1a9dce9..ec3ed2f1bf7f695b7fdfecbf1b907500d1492634 100644
--- a/src/killer_sokoban/AbstractField.java
+++ b/src/killer_sokoban/AbstractField.java
@@ -59,7 +59,7 @@ public abstract class AbstractField {
 		if(!isCorner) return;
 		
 		for(AbstractField neighbor : neighbours.values()) {
-			neighbor.setToCorner();
+			if(!neighbor.isCorner) neighbor.setToCorner();
 		}
 	}