diff --git a/.changeset/healthy-jokes-sing.md b/.changeset/healthy-jokes-sing.md
new file mode 100644
index 00000000000..3b48e7780e9
--- /dev/null
+++ b/.changeset/healthy-jokes-sing.md
@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Don't send `operationType` in the payload sent by `GraphQLWsLink`.
diff --git a/src/link/subscriptions/__tests__/graphqlWsLink.ts b/src/link/subscriptions/__tests__/graphqlWsLink.ts
index 92c32aebe3e..82c731f1722 100644
--- a/src/link/subscriptions/__tests__/graphqlWsLink.ts
+++ b/src/link/subscriptions/__tests__/graphqlWsLink.ts
@@ -6,7 +6,10 @@ import type { Observable } from "rxjs";
 
 import { CombinedGraphQLErrors } from "@apollo/client/errors";
 import { GraphQLWsLink } from "@apollo/client/link/subscriptions";
-import { executeWithDefaultContext as execute } from "@apollo/client/testing/internal";
+import {
+  executeWithDefaultContext as execute,
+  ObservableStream,
+} from "@apollo/client/testing/internal";
 
 const query = gql`
   query SampleQuery {
@@ -175,3 +178,31 @@ describe("GraphQLWSlink", () => {
     });
   });
 });
+
+// https://github.com/apollographql/apollo-client/issues/12946
+test("sends only known keys to the GraphQLWsLink", async () => {
+  const knownKeys = [
+    "query",
+    "variables",
+    "operationName",
+    "extensions",
+  ].sort();
+
+  type SubscribeFn = Client["subscribe"];
+  const subscribe = jest.fn<ReturnType<SubscribeFn>, Parameters<SubscribeFn>>(
+    (_payload, sink) => {
+      sink.complete();
+      return () => {};
+    }
+  );
+  const client = mockClient(subscribe);
+  const link = new GraphQLWsLink(client);
+
+  const stream = new ObservableStream(execute(link, { query: subscription }));
+  await stream.takeComplete();
+
+  expect(subscribe).toHaveBeenCalledTimes(1);
+
+  const payload = subscribe.mock.calls[0][0];
+  expect(Object.keys(payload).sort()).toStrictEqual(knownKeys);
+});
diff --git a/src/link/subscriptions/index.ts b/src/link/subscriptions/index.ts
index 7f6295117fe..2a3ab8e7e0c 100644
--- a/src/link/subscriptions/index.ts
+++ b/src/link/subscriptions/index.ts
@@ -79,8 +79,9 @@ export class GraphQLWsLink extends ApolloLink {
     operation: ApolloLink.Operation
   ): Observable<ApolloLink.Result> {
     return new Observable((observer) => {
+      const { query, variables, operationName, extensions } = operation;
       return this.client.subscribe<ApolloLink.Result>(
-        { ...operation, query: print(operation.query) },
+        { variables, operationName, extensions, query: print(query) },
         {
           next: observer.next.bind(observer),
           complete: observer.complete.bind(observer),