diff --git a/verify.py b/verify.py
index 38ddd0d..6d55ad1 100644
--- a/verify.py
+++ b/verify.py
@@ -86,6 +86,7 @@ def check_for_intersection(filename_a, filename_b):
         print("The following domains appear in both lists:")
         for line in sorted(intersection):
             print("* {}".format(line))
+        sys.exit(1)
 
 
 if __name__ == "__main__":