SpigotCore_Main/src/de/steamwar/command/SWCommandUtils.java

@@ -24,6 +24,7 @@ import org.bukkit.GameMode;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandMap;
 import org.bukkit.command.CommandSender;
+import org.bukkit.command.SimpleCommandMap;
 import org.bukkit.entity.Player;
 
 import java.lang.annotation.Annotation;
@@ -89,7 +90,7 @@ public class SWCommandUtils {
             throw new SecurityException("Oh shit. Commands cannot be registered.", exception);
         }
         try {
-            final Field knownCommandsField = commandMap.getClass().getDeclaredField("knownCommands");
+            final Field knownCommandsField = SimpleCommandMap.class.getDeclaredField("knownCommands");
             knownCommandsField.setAccessible(true);
             knownCommandMap = (Map<String, Command>) knownCommandsField.get(commandMap);
         } catch (NoSuchFieldException | IllegalAccessException exception) {