diff --git a/engine/src/main/battlecode/world/RobotControllerImpl.java b/engine/src/main/battlecode/world/RobotControllerImpl.java
index 07d96612..0633c0ce 100644
--- a/engine/src/main/battlecode/world/RobotControllerImpl.java
+++ b/engine/src/main/battlecode/world/RobotControllerImpl.java
@@ -610,6 +610,9 @@ private void assertCanUpgradeTower(MapLocation loc) throws GameActionException{
         assertCanActLocation(loc, GameConstants.BUILD_TOWER_RADIUS_SQUARED);
         InternalRobot robot = this.gameWorld.getRobot(loc);
 
+        if (robot == null){
+            throw new GameActionException(CANT_DO_THAT, "There is no robot at the location");
+        }
         if (!this.robot.getType().isTowerType()){ 
             throw new GameActionException(CANT_DO_THAT, "No tower at the location");
         }