diff --git a/testing/resources/duplicate_key_yaml.notyaml b/testing/resources/duplicate_key_yaml.notyaml
new file mode 100644
index 0000000..e682077
--- /dev/null
+++ b/testing/resources/duplicate_key_yaml.notyaml
@@ -0,0 +1,2 @@
+hello: "world"
+hello: "planet"
\ No newline at end of file
diff --git a/tests/check_yaml_test.py b/tests/check_yaml_test.py
index 54eb16e..ad059fa 100644
--- a/tests/check_yaml_test.py
+++ b/tests/check_yaml_test.py
@@ -27,6 +27,13 @@ def test_main_allow_multiple_documents(tmpdir):
     # should pass when we allow multiple documents
     assert not main(('--allow-multiple-documents', str(f)))
 
+def test_main_allow_duplicate_keys(tmpdir):
+    f = get_resource_path('duplicate_key_yaml.notyaml')
+    # should fail by default
+    assert main((str(f),))
+    # should pass when we allow duplicate keys
+    assert not main(('--allow-duplicate-keys', str(f)))
+
 
 def test_fails_even_with_allow_multiple_documents(tmpdir):
     f = tmpdir.join('test.yaml')