diff --git a/src/Tie/Codegen/Response.hs b/src/Tie/Codegen/Response.hs
index 710212e..117db53 100644
--- a/src/Tie/Codegen/Response.hs
+++ b/src/Tie/Codegen/Response.hs
@@ -71,7 +71,7 @@ codegenToResponses operationName responses defaultResponse =
         | Just {} <- jsonResponseContent =
           "(" <> "Data.Aeson.fromEncoding" <+> "(" <> "Data.Aeson.toEncoding" <+> "x" <> ")" <> ")"
         | otherwise =
-          mempty
+          "mempty"
 
       responseHeaders Response {jsonResponseContent}
         | Just {} <- jsonResponseContent =
diff --git a/test/golden/petstore.yaml.out b/test/golden/petstore.yaml.out
index 5d91400..3e96b1f 100644
--- a/test/golden/petstore.yaml.out
+++ b/test/golden/petstore.yaml.out
@@ -160,7 +160,7 @@ data CreatePetsResponse
 
 instance ToResponse CreatePetsResponse where
     toResponse (CreatePetsResponse201 ) =
-        Network.Wai.responseBuilder (toEnum 201) [] 
+        Network.Wai.responseBuilder (toEnum 201) [] mempty
     toResponse (CreatePetsDefaultResponse status x) =
         Network.Wai.responseBuilder status [(Network.HTTP.Types.hContentType, "application/json")] (Data.Aeson.fromEncoding (Data.Aeson.toEncoding x))
 ---------------------