diff --git a/gestioncof/forms.py b/gestioncof/forms.py
index 064eef8e..07b7cd89 100644
--- a/gestioncof/forms.py
+++ b/gestioncof/forms.py
@@ -200,9 +200,11 @@ class UserProfileForm(forms.ModelForm):
 
 class RegistrationUserForm(forms.ModelForm):
     def __init__(self, *args, **kw):
+        new_user = kw.get('instance') is None
         super(RegistrationUserForm, self).__init__(*args, **kw)
         self.fields['username'].help_text = ""
-        self.fields['username'].validators = [MinLengthValidator(9)]
+        if new_user:
+            self.fields['username'].validators = [MinLengthValidator(9)]
 
     class Meta:
         model = User