diff --git a/OpenRA.Game/Server/Server.cs b/OpenRA.Game/Server/Server.cs
index ed53f791a3..05578dc239 100644
--- a/OpenRA.Game/Server/Server.cs
+++ b/OpenRA.Game/Server/Server.cs
@@ -679,7 +679,7 @@ namespace OpenRA.Server
 				DropClient(c);
 
 			// Drop any players who are not ready
-			foreach (var c in Conns.Where(c => GetClient(c).IsInvalid))
+			foreach (var c in Conns.Where(c => GetClient(c).IsInvalid).ToArray())
 			{
 				SendOrderTo(c, "ServerError", "You have been kicked from the server!");
 				DropClient(c);