diff --git a/add.py b/add.py
index 5c9b51c..7d58d92 100644
--- a/add.py
+++ b/add.py
@@ -1,5 +1,5 @@
 def add(x: int, y: int) -> int:
     """Returns the sum of two integers."""
-    #if not isinstance(x, int) or not isinstance(y,int):
-    #    raise TypeError("Both arguments musst be integers")
+    if not isinstance(x, int) or not isinstance(y,int):
+        raise TypeError("Both arguments musst be integers")
     return x + y