diff --git a/collector/storage/models.py b/collector/storage/models.py
index c7a80db..4e9da9f 100755
--- a/collector/storage/models.py
+++ b/collector/storage/models.py
@@ -147,9 +147,9 @@ class Document(models.Model):
     class Meta:
         db_table = 'document'
         ordering = ['id']
-        # constraints = [
-        #     models.UniqueConstraint(fields=['name', 'sequence'], name='unique subdocument sequence')
-        # ]
+        constraints = [
+            models.UniqueConstraint(fields=['name', 'sequence'], name='unique subdocument sequence')
+        ]
 
     def __str__(self):
         return f'{self.name}-{self.id}'
diff --git a/collector/storage/views.py b/collector/storage/views.py
index 2094574..cc49f44 100755
--- a/collector/storage/views.py
+++ b/collector/storage/views.py
@@ -1158,7 +1158,8 @@ def change_doc_type(doc, target_type):
                                          processing_status=doc.processing_status,
                                          new=doc.new,
                                          unk_coverage=doc.unk_coverage,
-                                         sequence=doc.sequence)
+                                         sequence=1000000)
+    seq = doc.sequence
     new_doc.keywords.add(*doc.keywords.all())
     subdocs = Document.objects.filter(parent=doc)
     for subdoc in subdocs:
@@ -1178,6 +1179,9 @@ def change_doc_type(doc, target_type):
         a.save()
 
     doc.delete()
+    new_doc.sequence = seq
+    new_doc.save()
+
     return new_doc
 
 
@@ -1197,6 +1201,9 @@ class DocTypeView(UpdateView):
         context = super().get_context_data(**kwargs)
         context['title'] = 'Zmiana typu dokumentu'
         context['submit_btn_text'] = 'Zmień'
+        if self.object.parent is None:
+            messages.warning(self.request, 'Uwaga! Zmiana typu dokumentu głównego nie powoduje zmiany typów '
+                                           'poddokumentów. Można je zmienić nastomiast manualnie.')
         messages.warning(self.request, 'Uwaga! Zmiana typu dokumentu może spowodować usunięcie danych typowych dla '
                                        'tego typu.')
         return context