diff --git a/src/api/v1/users/serializers.py b/src/api/v1/users/serializers.py
index cb2a1de..97736ea 100644
--- a/src/api/v1/users/serializers.py
+++ b/src/api/v1/users/serializers.py
@@ -57,7 +57,7 @@ def validate_invited_by_code(self, value):
         """
         user = self.instance
 
-        if value == user.invite_code:
+        if value.lower() == user.invite_code.lower():
             raise serializers.ValidationError('Cannot specify your own code.')
 
         try:
diff --git a/src/api/v1/users/views.py b/src/api/v1/users/views.py
index b70cce0..b85e5ec 100644
--- a/src/api/v1/users/views.py
+++ b/src/api/v1/users/views.py
@@ -241,6 +241,11 @@ def post(self, request):
                     {'invited_by_code': 'Неверный реферальный код.'},
                     status=status.HTTP_403_FORBIDDEN
                 )
+            if user.first().invite_code.lower() == invited_by_code.lower():
+                return Response(
+                    {'invited_by_code': 'Нельзя использовать свой код.'},
+                    status=status.HTTP_403_FORBIDDEN
+                )
             user_data['invited_by_code'] = invited_by_code
 
         user, _ = User.objects.update_or_create(
diff --git a/src/users/models.py b/src/users/models.py
index 0152990..17eeefa 100644
--- a/src/users/models.py
+++ b/src/users/models.py
@@ -111,7 +111,7 @@ def clean(self):
 
         """
         if self.invited_by_code:
-            if self.invited_by_code == self.invite_code:
+            if self.invited_by_code.lower() == self.invite_code.lower():
                 raise ValidationError(
                     {'invited_by_code': 'Cannot specify your own code.'}
                 )