proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientConfigSessionHandler.java

@@ -79,6 +79,11 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
     configSwitchFuture = new CompletableFuture<>();
   }
 
+  @Override
+  public void deactivated() {
+    configurationFuture = null;
+  }
+
   @Override
   public boolean handle(final KeepAlivePacket packet) {
     player.forwardKeepAlive(packet);