diff --git a/src/PubSubClient.php b/src/PubSubClient.php
index 926ce1b..8586a27 100644
--- a/src/PubSubClient.php
+++ b/src/PubSubClient.php
@@ -196,6 +196,10 @@ public function __construct(array $config = [])
             $config['universeDomain']
         );
 
+        if ($config['transport'] !== 'rest') {
+            $this->encode = true;
+        }
+
         $this->projectId = $this->detectProjectId($config);
 
         $this->clientConfig = $config;