diff --git a/sapl/materia/forms.py b/sapl/materia/forms.py
index 0e841504b..9a1e4eda7 100644
--- a/sapl/materia/forms.py
+++ b/sapl/materia/forms.py
@@ -202,7 +202,8 @@ class MateriaLegislativaForm(ModelForm):
                                                         widget=forms.HiddenInput())
             self.fields['autor'] = forms.CharField(required=False,
                                                    widget=forms.HiddenInput())
-            self.fields['numero_protocolo'].widget.attrs['readonly'] = True
+            if kwargs['instance'].numero_protocolo:
+                self.fields['numero_protocolo'].widget.attrs['readonly'] = True
 
     def clean(self):
         super(MateriaLegislativaForm, self).clean()