diff --git a/src/main/java/dotsandboxes/DotsAndBoxesGrid.java b/src/main/java/dotsandboxes/DotsAndBoxesGrid.java
index 32667af6c63a0287bd4f91c37682acb30c08e9a4..cbcc9f21cd461640fc1ec3255df0d319fc07a0d2 100644
--- a/src/main/java/dotsandboxes/DotsAndBoxesGrid.java
+++ b/src/main/java/dotsandboxes/DotsAndBoxesGrid.java
@@ -1,6 +1,5 @@
 package dotsandboxes;
 
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Observer;
@@ -113,7 +112,10 @@ public class DotsAndBoxesGrid {
 
         // A box is complete if the north and south horizontals and the east and west verticals have all been drawn.
         // FIXME: You'll need to fix this code (after writing a test first).
-        return true;
+        if (getHorizontal(x,y) && getVertical(x,y)) {
+            return true;   
+        }
+        return false;   
     }
 
     /** Tries to claim a box for a player. If the box is complete, sets the ownership and returns true. */
@@ -141,6 +143,9 @@ public class DotsAndBoxesGrid {
         }
 
         // FIXME: You need to throw an exception if the line was already drawn.
+        if (getHorizontal(x,y)) {
+            throw new IllegalStateException(String.format("line x=%d,y=%d was already drawn",x,y));
+        }
 
         this.horizontals[x][y] = true;