diff --git a/src/Client.php b/src/Client.php
index 40aebe3..9303184 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -311,12 +311,12 @@ public function containerStart($container, $config = array())
     /**
      * Stop the container id
      *
-     * @param string $container container ID
-     * @param int    $t         number of seconds to wait before killing the container
+     * @param string   $container container ID
+     * @param null|int $t         (optional) number of seconds to wait before killing the container
      * @return Promise Promise<null>
      * @link https://docs.docker.com/reference/api/docker_remote_api_v1.15/#stop-a-container
      */
-    public function containerStop($container, $t)
+    public function containerStop($container, $t = null)
     {
         return $this->browser->post(
             $this->uri->expand(
@@ -332,12 +332,12 @@ public function containerStop($container, $t)
     /**
      * Restart the container id
      *
-     * @param string $container container ID
-     * @param int    $t         number of seconds to wait before killing the container
+     * @param string   $container container ID
+     * @param null|int $t         (optional) number of seconds to wait before killing the container
      * @return Promise Promise<null>
      * @link https://docs.docker.com/reference/api/docker_remote_api_v1.15/#restart-a-container
      */
-    public function containerRestart($container, $t)
+    public function containerRestart($container, $t = null)
     {
         return $this->browser->post(
             $this->uri->expand(
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index 192e029..7aa7992 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -143,6 +143,13 @@ public function testContainerStart()
     }
 
     public function testContainerStop()
+    {
+        $this->expectRequestFlow('post', '/containers/123/stop', $this->createResponse(), 'expectEmpty');
+
+        $this->expectPromiseResolveWith('', $this->client->containerStop(123));
+    }
+
+    public function testContainerStopTimeout()
     {
         $this->expectRequestFlow('post', '/containers/123/stop?t=10', $this->createResponse(), 'expectEmpty');
 
@@ -150,6 +157,13 @@ public function testContainerStop()
     }
 
     public function testContainerRestart()
+    {
+        $this->expectRequestFlow('post', '/containers/123/restart', $this->createResponse(), 'expectEmpty');
+
+        $this->expectPromiseResolveWith('', $this->client->containerRestart(123));
+    }
+
+    public function testContainerRestartTimeout()
     {
         $this->expectRequestFlow('post', '/containers/123/restart?t=10', $this->createResponse(), 'expectEmpty');