diff --git a/GameMap.py b/GameMap.py
index 073f833..0c62b73 100644
--- a/GameMap.py
+++ b/GameMap.py
@@ -21,7 +21,7 @@ class GameMap:
         if x <= max_size_x or y <= max_size_y:
             self.data[(x,y)] = player
         else:
-            raise IndexError()
+            raise IndexError("Mark added beyond preset max values (max_x - " + self.max_size_x + ", max_y - " + self.max_size_y + ".")
     
     
     def equal(what, to):