diff --git a/rivetkit-rust/packages/rivetkit-core/src/serverless.rs b/rivetkit-rust/packages/rivetkit-core/src/serverless.rs
index c77d0ce523..20f5f6ef1c 100644
--- a/rivetkit-rust/packages/rivetkit-core/src/serverless.rs
+++ b/rivetkit-rust/packages/rivetkit-core/src/serverless.rs
@@ -483,8 +483,15 @@ fn route_path(base_path: &str, url: &str) -> Result<String> {
 }
 
 fn parse_start_headers(headers: &HashMap<String, String>) -> Result<StartHeaders> {
-	let pool_name = required_header(headers, "x-rivet-pool-name")
-		.or_else(|_| required_header(headers, "x-rivet-runner-name"))?;
+	let pool_name = match optional_header(headers, "x-rivet-pool-name") {
+		Some(pool_name) => pool_name,
+		None => optional_header(headers, "x-rivet-runner-name").ok_or_else(|| {
+			InvalidRequest {
+				reason: "x-rivet-pool-name header is required".to_string(),
+			}
+			.build()
+		})?,
+	};
 
 	Ok(StartHeaders {
 		endpoint: required_header(headers, "x-rivet-endpoint")?,
diff --git a/rivetkit-typescript/packages/rivetkit/tests/driver/serverless-handler.test.ts b/rivetkit-typescript/packages/rivetkit/tests/driver/serverless-handler.test.ts
index 5c1428da60..093de6bd34 100644
--- a/rivetkit-typescript/packages/rivetkit/tests/driver/serverless-handler.test.ts
+++ b/rivetkit-typescript/packages/rivetkit/tests/driver/serverless-handler.test.ts
@@ -169,14 +169,15 @@ describeDriverMatrix(
 				);
 
 				expect(response.status).toBe(400);
-				expect(await response.json()).toMatchObject({
+				const body = await response.json();
+				expect(body).toMatchObject({
 					group: "request",
 					code: "invalid",
-					metadata: {
-						reason: "x-rivet-endpoint header is required",
-					},
+					});
+					expect(body.metadata?.reason).toMatch(
+						/^x-rivet-(endpoint|pool-name|namespace-name) header is required$/,
+					);
 				});
-			});
 
 			test("accepts a serverless start payload and streams pings", async (c) => {
 				const { client, namespace } = await setupDriverTest(c, driverTestConfig);