diff --git a/src/Client.php b/src/Client.php
index 3064342..bd03c67 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -1280,7 +1280,7 @@ public function execCreate($container, $cmd, $tty = false, $stdin = false, $stdo
                 'AttachStdin' => !!$stdin,
                 'AttachStdout' => !!$stdout,
                 'AttachStderr' => !!$stderr,
-                'User' => $user,
+                'User' => (string) $user,
                 'Privileged' => !!$privileged,
             )
         )->then(array($this->parser, 'expectJson'));
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index 8f3ff1b..7a06f78 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -655,6 +655,15 @@ public function testExecCreateStringCommand()
         $this->expectPromiseResolveWith($json, $this->client->execCreate(123, 'env'));
     }
 
+    public function testExecCreateWithNumericUser()
+    {
+        $json = array();
+        $this->browser->expects($this->once())->method('post')->with('containers/123/exec', $this->anything(), '{"Cmd":["env"],"Tty":false,"AttachStdin":false,"AttachStdout":true,"AttachStderr":true,"User":"1000","Privileged":false}')->willReturn(\React\Promise\resolve($this->createResponseJson($json)));
+        $this->parser->expects($this->once())->method('expectJson')->willReturn($json);
+
+        $this->expectPromiseResolveWith($json, $this->client->execCreate(123, array('env'), false, false, true, true, 1000));
+    }
+
     public function testExecDetached()
     {
         $body = '';