diff --git a/handwritten/storage/src/file.ts b/handwritten/storage/src/file.ts
index 27765d935a99..d5aa40bf96e1 100644
--- a/handwritten/storage/src/file.ts
+++ b/handwritten/storage/src/file.ts
@@ -3236,6 +3236,7 @@ class File extends ServiceObject<File, FileMetadata> {
       contentMd5: cfg.contentMd5,
       contentType: cfg.contentType,
       host: cfg.host,
+      signingEndpoint: cfg.signingEndpoint,
     };
 
     if (cfg.cname) {
diff --git a/handwritten/storage/src/signer.ts b/handwritten/storage/src/signer.ts
index a657cef6133d..ba5c17c04b75 100644
--- a/handwritten/storage/src/signer.ts
+++ b/handwritten/storage/src/signer.ts
@@ -25,7 +25,7 @@ type GoogleAuthLike = Pick<GoogleAuth, 'getCredentials' | 'sign'>;
  * @deprecated Use {@link GoogleAuth} instead
  */
 export interface AuthClient {
-  sign(blobToSign: string): Promise<string>;
+  sign(blobToSign: string, signingEndpoint?: string): Promise<string>;
   getCredentials(): Promise<{
     client_email?: string;
   }>;
diff --git a/handwritten/storage/test/file.ts b/handwritten/storage/test/file.ts
index 26823995b907..d9f9185a16e8 100644
--- a/handwritten/storage/test/file.ts
+++ b/handwritten/storage/test/file.ts
@@ -3794,11 +3794,30 @@ describe('File', () => {
           contentType: config.contentType,
           cname: CNAME,
           virtualHostedStyle: true,
+          signingEndpoint: undefined,
         });
         done();
       });
     });
 
+    it('should pass signingEndpoint to URLSigner', done => {
+      const signingEndpoint = 'https://my-endpoint.com';
+      const config = {
+        ...SIGNED_URL_CONFIG,
+        signingEndpoint,
+      };
+
+      file.getSignedUrl(config, (err: Error | null) => {
+        assert.ifError(err);
+        const getSignedUrlArgs = signerGetSignedUrlStub.getCall(0).args;
+        assert.strictEqual(
+          getSignedUrlArgs[0]['signingEndpoint'],
+          signingEndpoint
+        );
+        done();
+      });
+    });
+
     it('should add "x-goog-resumable: start" header if action is resumable', done => {
       SIGNED_URL_CONFIG.action = 'resumable';
       SIGNED_URL_CONFIG.extensionHeaders = {