diff --git a/src/Transport/Socket.php b/src/Transport/Socket.php
index 8496a80f..bdf83063 100644
--- a/src/Transport/Socket.php
+++ b/src/Transport/Socket.php
@@ -119,7 +119,7 @@ public function request($method, UriInterface $uri, $data = null, array $headers
 		}
 
 		// Configure protocol version, use transport's default if not set otherwise.
-		$protocolVersion = isset($this->options['protocolVersion']) ? $this->options['protocolVersion'] : '1.1';
+		$protocolVersion = isset($this->options['protocolVersion']) ? $this->options['protocolVersion'] : '1.0';
 
 		// Build the request payload.
 		$request   = array();