diff --git a/moto/apigateway/responses.py b/moto/apigateway/responses.py
index d8f3ed505..0454ae58e 100644
--- a/moto/apigateway/responses.py
+++ b/moto/apigateway/responses.py
@@ -449,7 +449,7 @@ class APIGatewayResponse(BaseResponse):
             except ApiKeyAlreadyExists as error:
                 return (
                     error.code,
-                    self.headers,
+                    {},
                     '{{"message":"{0}","code":"{1}"}}'.format(
                         error.message, error.error_type
                     ),
diff --git a/tests/test_apigateway/test_apigateway.py b/tests/test_apigateway/test_apigateway.py
index d79851ab0..c58d644fa 100644
--- a/tests/test_apigateway/test_apigateway.py
+++ b/tests/test_apigateway/test_apigateway.py
@@ -1858,6 +1858,23 @@ def test_create_api_key():
     client.create_api_key.when.called_with(**payload).should.throw(ClientError)
 
 
+@mock_apigateway
+def test_create_api_headers():
+    region_name = "us-west-2"
+    client = boto3.client("apigateway", region_name=region_name)
+
+    apikey_value = "12345"
+    apikey_name = "TESTKEY1"
+    payload = {"value": apikey_value, "name": apikey_name}
+
+    client.create_api_key(**payload)
+    with assert_raises(ClientError) as ex:
+        client.create_api_key(**payload)
+    ex.exception.response["Error"]["Code"].should.equal("ConflictException")
+    if not settings.TEST_SERVER_MODE:
+        ex.exception.response["ResponseMetadata"]["HTTPHeaders"].should.equal({})
+
+
 @mock_apigateway
 def test_api_keys():
     region_name = "us-west-2"