Fix

src/main/java/systems/brn/justteleportalready/mixin/JustTeleportAlreadyMixin.java

@@ -21,7 +21,8 @@ public class JustTeleportAlreadyMixin {
         cir.setReturnValue(world.getGameRules().getInt(Entity_Portal_Cooldown));
     }
 
-    @Shadow protected int portalCooldown;
+    @Shadow
+    private int portalCooldown;
     @Inject(method = "tickPortalCooldown", at = @At(value = "RETURN"))
     private void tickPortalCooldown(CallbackInfo ci) {
         int maxCooldown = world.getGameRules().getInt(Entity_Portal_Cooldown);

src/main/resources/justteleportalready.mixins.json

@@ -4,7 +4,8 @@
   "package": "systems.brn.justteleportalready.mixin",
   "compatibilityLevel": "JAVA_21",
   "mixins": [
-    "DontHurtMePearlMixin"
+    "DontHurtMePearlMixin",
+    "JustTeleportAlreadyMixin"
   ],
   "injectors": {
     "defaultRequire": 1