diff --git a/__init__.py b/__init__.py
index 486b507..9ce7fb7 100644
--- a/__init__.py
+++ b/__init__.py
@@ -23,13 +23,15 @@ Classes = (BLENDERGPT_PT_PANEL, BLENDERGPT_OT_DEL_ALL_MSG, BLENDERGPT_OT_DEL_MSG
 
 def register():
     for cls in Classes:
-        bpy.utils.register_class(cls)
+        if cls.__name__ not in bpy.types.__dict__:
+            bpy.utils.register_class(cls)
 
     props_initialization()
 
 
 def unregister():
     for cls in Classes:
-        bpy.utils.unregister_class(cls)
+        if cls.__name__ in bpy.types.__dict__:
+            bpy.utils.unregister_class(cls)
 
     props_clear()