diff --git a/src/main/java/cn/nukkit/command/Command.java b/src/main/java/cn/nukkit/command/Command.java
index fbbd4954eb7..4fa618b27e5 100644
--- a/src/main/java/cn/nukkit/command/Command.java
+++ b/src/main/java/cn/nukkit/command/Command.java
@@ -211,7 +211,7 @@ public boolean unregister(CommandMap commandMap) {
     }
 
     public boolean allowChangesFrom(CommandMap commandMap) {
-        return commandMap != null && !commandMap.equals(this.commandMap);
+        return this.commandMap == null || this.commandMap.equals(commandMap);
     }
 
     public boolean isRegistered() {
diff --git a/src/main/java/cn/nukkit/command/defaults/EffectCommand.java b/src/main/java/cn/nukkit/command/defaults/EffectCommand.java
index f7b3f68b494..8b5877e0394 100644
--- a/src/main/java/cn/nukkit/command/defaults/EffectCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/EffectCommand.java
@@ -22,7 +22,7 @@
  * Created by Snake1999 and Pub4Game on 2016/1/23.
  * Package cn.nukkit.command.defaults in project nukkit.
  */
-public class EffectCommand extends Command {
+public class EffectCommand extends VanillaCommand {
     public EffectCommand(String name) {
         super(name, "%nukkit.command.effect.description", "%commands.effect.usage");
         this.setPermission("nukkit.command.effect");
diff --git a/src/main/java/cn/nukkit/command/defaults/XpCommand.java b/src/main/java/cn/nukkit/command/defaults/XpCommand.java
index 9ca01f11b92..1b5a9e407fc 100644
--- a/src/main/java/cn/nukkit/command/defaults/XpCommand.java
+++ b/src/main/java/cn/nukkit/command/defaults/XpCommand.java
@@ -12,7 +12,7 @@
  * Created by Snake1999 on 2016/1/22.
  * Package cn.nukkit.command.defaults in project nukkit.
  */
-public class XpCommand extends Command {
+public class XpCommand extends VanillaCommand {
     public XpCommand(String name) {
         super(name, "%nukkit.command.xp.description", "%commands.xp.usage");
         this.setPermission("nukkit.command.xp");