diff --git a/Facepunch.Steamworks/Client.cs b/Facepunch.Steamworks/Client.cs
index e46e5e4..32419bd 100644
--- a/Facepunch.Steamworks/Client.cs
+++ b/Facepunch.Steamworks/Client.cs
@@ -65,6 +65,11 @@ public partial class Client : BaseSteamworks
 
         public Client( uint appId )
         {
+            if ( Instance != null )
+            {
+                throw new System.Exception( "Only one Facepunch.Steamworks.Client can exist - dispose the old one before trying to create a new one." );
+            }
+
             Instance = this;
             native = new Interop.NativeInterface();
 
diff --git a/Facepunch.Steamworks/Server.cs b/Facepunch.Steamworks/Server.cs
index da274e0..01c21d4 100644
--- a/Facepunch.Steamworks/Server.cs
+++ b/Facepunch.Steamworks/Server.cs
@@ -26,6 +26,11 @@ public partial class Server : BaseSteamworks
         /// </summary>
         public Server( uint appId, ServerInit init )
         {
+            if ( Instance != null )
+            {
+                throw new System.Exception( "Only one Facepunch.Steamworks.Server can exist - dispose the old one before trying to create a new one." );
+            }
+
             Instance = this;
             native = new Interop.NativeInterface();