diff --git a/Assets/Mirror/Runtime/Transport/MultiplexTransport.cs b/Assets/Mirror/Runtime/Transport/MultiplexTransport.cs
index 806cbfccd..787ae8fa1 100644
--- a/Assets/Mirror/Runtime/Transport/MultiplexTransport.cs
+++ b/Assets/Mirror/Runtime/Transport/MultiplexTransport.cs
@@ -95,7 +95,7 @@ public override bool ClientConnected()
 
         public override void ClientDisconnect()
         {
-            if (available != null)
+            if ((object)available != null)
                 available.ClientDisconnect();
         }
 
diff --git a/Assets/Mirror/Tests/MultiplexTest.cs b/Assets/Mirror/Tests/MultiplexTest.cs
index ad8e1f8a2..231a33a2d 100644
--- a/Assets/Mirror/Tests/MultiplexTest.cs
+++ b/Assets/Mirror/Tests/MultiplexTest.cs
@@ -103,5 +103,16 @@ public void TestConnected()
 
             Assert.That(transport.ClientConnected());
         }
+
+        [Test]
+        public void TestDisconnect()
+        {
+            transport1.Available().Returns(true);
+            transport.ClientConnect("some.server.com");
+
+            transport.ClientDisconnect();
+
+            transport1.Received().ClientDisconnect();
+        }
     }
 }