diff --git a/response.ts b/response.ts
index 2164aac..fa5bb0f 100644
--- a/response.ts
+++ b/response.ts
@@ -157,6 +157,9 @@ export async function createResponse(
 
     return new Response(JSON.stringify(result), {
       status: Status.BadRequest,
+      headers: {
+        "content-type": withCharset(accept),
+      },
     });
   }
 
diff --git a/response_test.ts b/response_test.ts
index 467d927..7d9465f 100644
--- a/response_test.ts
+++ b/response_test.ts
@@ -327,7 +327,7 @@ describe("createResponse", () => {
           {
             status: Status.BadRequest,
             headers: {
-              "content-type": "text/plain;charset=UTF-8",
+              "content-type": "application/graphql-response+json;charset=UTF-8",
             },
           },
         ),