diff --git a/spec/common/providers/https.spec.ts b/spec/common/providers/https.spec.ts
index 050577564..55f698575 100644
--- a/spec/common/providers/https.spec.ts
+++ b/spec/common/providers/https.spec.ts
@@ -802,6 +802,31 @@ describe("onCallHandler", () => {
       const data = [`data: {"error":{"message":"INTERNAL","status":"INTERNAL"}}`];
       expect(resp.body).to.equal([...data, ""].join("\n"));
     });
+
+    it("always returns error for v1 callables", async () => {
+      const mockReq = mockRequest(
+        { message: "hello streaming" },
+        "application/json",
+        {},
+        { accept: "text/event-stream" }
+      ) as any;
+      const fn = https.onCallHandler(
+        {
+          cors: { origin: true, methods: "POST" },
+        },
+        () => {
+          return "hello world";
+        },
+        "gcfv1"
+      );
+      const resp = await runHandler(fn, mockReq);
+      expect(JSON.parse(resp.body)).to.deep.equal({
+        error: {
+          status: "INVALID_ARGUMENT",
+          message: "Unsupported Accept header 'text/event-stream'",
+        },
+      });
+    });
   });
 });
 
diff --git a/src/common/providers/https.ts b/src/common/providers/https.ts
index d10696837..d798a2579 100644
--- a/src/common/providers/https.ts
+++ b/src/common/providers/https.ts
@@ -782,6 +782,12 @@ function wrapOnCallHandler<Req = any, Res = any>(
       }
 
       const acceptsStreaming = req.header("accept") === "text/event-stream";
+
+      if (acceptsStreaming && version === "gcfv1") {
+        // streaming responses are not supported in v1 callable
+        throw new HttpsError("invalid-argument", "Unsupported Accept header 'text/event-stream'");
+      }
+
       const data: Req = decode(req.body.data);
       let result: Res;
       if (version === "gcfv1") {
@@ -832,7 +838,7 @@ function wrapOnCallHandler<Req = any, Res = any>(
 
       const { status } = httpErr.httpErrorCode;
       const body = { error: httpErr.toJSON() };
-      if (req.header("accept") === "text/event-stream") {
+      if (version === "gcfv2" && req.header("accept") === "text/event-stream") {
         res.send(encodeSSE(body));
       } else {
         res.status(status).send(body);