diff --git a/Mage.Server/src/main/java/mage/server/Session.java b/Mage.Server/src/main/java/mage/server/Session.java
index 0a025f3d731..3d0bbad25c1 100644
--- a/Mage.Server/src/main/java/mage/server/Session.java
+++ b/Mage.Server/src/main/java/mage/server/Session.java
@@ -157,7 +157,7 @@ public class Session {
 			call.setMessageId(messageId++);
 			callbackHandler.handleCallbackOneway(new Callback(call));
 		} catch (HandleCallbackException ex) {
-			logger.fatal("Session fireCallback error", ex);
+			logger.fatal("Session fireCallback error: " + ex.getMessage(), ex);
 			disconnect();
 		}
 	}
diff --git a/Mage.Server/src/main/java/mage/server/UserManager.java b/Mage.Server/src/main/java/mage/server/UserManager.java
index 8ff58004e0f..c5de8f16c78 100644
--- a/Mage.Server/src/main/java/mage/server/UserManager.java
+++ b/Mage.Server/src/main/java/mage/server/UserManager.java
@@ -100,12 +100,14 @@ public class UserManager {
 	}
 	
 	public void disconnect(UUID userId) {
-        ChatManager.getInstance().removeUser(userId);
-		if (users.containsKey(userId)) {
-            logger.info("user disconnected " + userId);
-			users.get(userId).setSessionId("");
-			ChatManager.getInstance().broadcast(userId, "has lost connection", MessageColor.BLACK);
-		}
+        if (userId != null) {
+            ChatManager.getInstance().removeUser(userId);
+            if (users.containsKey(userId)) {
+                logger.info("user disconnected " + userId);
+                users.get(userId).setSessionId("");
+                ChatManager.getInstance().broadcast(userId, "has lost connection", MessageColor.BLACK);
+            }
+        }
 	}
 	
 	public boolean isAdmin(UUID userId) {