diff --git a/lesson-2/chapter-8/zombiefeeding.sol b/lesson-2/chapter-8/zombiefeeding.sol
index 5de9e21..48cf4ad 100644
--- a/lesson-2/chapter-8/zombiefeeding.sol
+++ b/lesson-2/chapter-8/zombiefeeding.sol
@@ -5,9 +5,9 @@ contract ZombieFeeding is ZombieFactory {
   function feedAndMultiply(uint _zombieId, uint _targetDna) public {
     require(msg.sender == zombieToOwner[_zombieId]);
     Zombie storage myZombie = zombies[_zombieId];
-    _targetDna = _targetDna % dnaModulus;
+    require(_targetDna == _targetDna % dnaModulus);
     uint newDna = (myZombie.dna + _targetDna) / 2;
     _createZombie("NoName", newDna);
   }
 
-}
\ No newline at end of file
+}