diff --git a/src/v1beta1/speech_translation_service_client.ts b/src/v1beta1/speech_translation_service_client.ts
index 9a73eb9..85fa706 100644
--- a/src/v1beta1/speech_translation_service_client.ts
+++ b/src/v1beta1/speech_translation_service_client.ts
@@ -162,7 +162,8 @@ export class SpeechTranslationServiceClient {
     // Provide descriptors for these.
     this.descriptors.stream = {
       streamingTranslateSpeech: new this._gaxModule.StreamDescriptor(
-        gax.StreamType.BIDI_STREAMING
+        gax.StreamType.BIDI_STREAMING,
+        opts.fallback === 'rest'
       ),
     };