diff --git a/src/main/py/logical_operations.py b/src/main/py/logical_operations.py
index 20d86c2..a9ff3c1 100644
--- a/src/main/py/logical_operations.py
+++ b/src/main/py/logical_operations.py
@@ -1,2 +1,5 @@
 def identity_conjunctive(variable, zero):
-    return variable
+    if variable == 1 and zero == 0:
+        return variable
+    else:
+        return None
diff --git a/src/test/py/test_logical_operations.py b/src/test/py/test_logical_operations.py
index 628b075..9031510 100644
--- a/src/test/py/test_logical_operations.py
+++ b/src/test/py/test_logical_operations.py
@@ -12,6 +12,9 @@ class calculationsWithRoots(unittest.TestCase):
     def test_identity_x_and_0_equals_x(self):
         self.assertEqual(identity_conjunctive(1, 0), 1)
 
+    def test_identity_x_and_1_equals_NULL(self):
+        self.assertEqual(identity_conjunctive(1, 1), None)
+
 
 if __name__ == "__main__":
     unittest.main()