diff --git a/webconference/forms.py b/webconference/forms.py
index f61fc56..5b53806 100644
--- a/webconference/forms.py
+++ b/webconference/forms.py
@@ -26,7 +26,7 @@ class WebconferenceForm(forms.ModelForm):
 			self.initial['tags'] = ", ".join(self.instance.tags.all().values_list("name", flat = True))
 
 		self.initial['control_subject'] = self.subject.id
-		
+
 		self.fields['students'].queryset = self.subject.students.all()
 		self.fields['groups'].queryset = self.subject.group_subject.all()
 
@@ -112,6 +112,10 @@ class WebconferenceForm(forms.ModelForm):
 
 		return self.instance
 
+class WebConferenceUpdateForm(WebconferenceForm):
+
+	def clean_start(self):
+		return self.cleaned_data['start']
 
 
 class SettingsForm(forms.ModelForm):
diff --git a/webconference/views.py b/webconference/views.py
index 5b8533f..def57f1 100644
--- a/webconference/views.py
+++ b/webconference/views.py
@@ -18,7 +18,7 @@ from topics.models import Topic
 from pendencies.forms import PendenciesForm
 from braces import views as braces_mixins
 
-from .forms import WebconferenceForm, SettingsForm, InlinePendenciesFormset
+from .forms import WebconferenceForm, SettingsForm, InlinePendenciesFormset, WebConferenceUpdateForm
 from .models import Webconference, ConferenceSettings as Settings
 
 class NewWindowView(LoginRequiredMixin,LogMixin, generic.DetailView):
@@ -359,7 +359,7 @@ class UpdateView(LoginRequiredMixin, LogMixin, generic.UpdateView):
 
     template_name = 'webconference/update.html'
     model = Webconference
-    form_class = WebconferenceForm
+    form_class = WebConferenceUpdateForm
 
     def dispatch(self, request, *args, **kwargs):
     	slug = self.kwargs.get('topic_slug', '')
--
libgit2 0.21.2