diff --git a/src/Handshake/ServerNegotiator.php b/src/Handshake/ServerNegotiator.php
index 7929f5f..2a6b2cd 100644
--- a/src/Handshake/ServerNegotiator.php
+++ b/src/Handshake/ServerNegotiator.php
@@ -23,8 +23,9 @@ class ServerNegotiator implements NegotiatorInterface {
     public function __construct(
         RequestVerifier $requestVerifier,
         ResponseFactoryInterface $responseFactory,
-        $enablePerMessageDeflate = false
+        $enablePerMessageDeflate = null
     ) {
+        if ($enablePerMessageDeflate == null) $enablePerMessageDeflate = false;
         $this->verifier = $requestVerifier;
         $this->responseFactory = $responseFactory;