diff --git a/ietf/meeting/helpers.py b/ietf/meeting/helpers.py
index e3ecc678e..143a65351 100644
--- a/ietf/meeting/helpers.py
+++ b/ietf/meeting/helpers.py
@@ -300,28 +300,6 @@ def session_constraint_expire(request,session):
 # -------------------------------------------------
 
 
-def assign_interim_session(form):
-    """Helper function to create a timeslot and assign the interim session"""
-    time = datetime.datetime.combine(
-        form.cleaned_data['date'],
-        form.cleaned_data['time'])
-    session = form.instance
-    if session.official_timeslotassignment():
-        slot = session.official_timeslotassignment().timeslot
-        slot.time = time
-        slot.save()
-    else:
-        slot = TimeSlot.objects.create(
-            meeting=session.meeting,
-            type_id="session",
-            duration=session.requested_duration,
-            time=time)
-        SchedTimeSessAssignment.objects.create(
-            timeslot=slot,
-            session=session,
-            schedule=session.meeting.agenda)
-
-
 def can_approve_interim_request(meeting, user):
     '''Returns True if the user has permissions to approve an interim meeting request'''
     if meeting.type.slug != 'interim':
@@ -657,6 +635,29 @@ def sessions_post_save(forms):
         if not form.has_changed():
             continue
         if ('date' in form.changed_data) or ('time' in form.changed_data):
-            assign_interim_session(form)
+            update_interim_session_assignment(form)
         if 'agenda' in form.changed_data:
             form.save_agenda()
+
+
+def update_interim_session_assignment(form):
+    """Helper function to create / update timeslot assigned to interim session"""
+    time = datetime.datetime.combine(
+        form.cleaned_data['date'],
+        form.cleaned_data['time'])
+    session = form.instance
+    if session.official_timeslotassignment():
+        slot = session.official_timeslotassignment().timeslot
+        slot.time = time
+        slot.duration = session.requested_duration
+        slot.save()
+    else:
+        slot = TimeSlot.objects.create(
+            meeting=session.meeting,
+            type_id="session",
+            duration=session.requested_duration,
+            time=time)
+        SchedTimeSessAssignment.objects.create(
+            timeslot=slot,
+            session=session,
+            schedule=session.meeting.agenda)
diff --git a/ietf/meeting/tests_views.py b/ietf/meeting/tests_views.py
index 5e7f73d02..6511eb238 100644
--- a/ietf/meeting/tests_views.py
+++ b/ietf/meeting/tests_views.py
@@ -1280,12 +1280,13 @@ class InterimTests(TestCase):
         form_initial = r.context['form'].initial
         formset_initial =  r.context['formset'].forms[0].initial
         new_time = formset_initial['time'] + datetime.timedelta(hours=1)
+        new_duration = formset_initial['requested_duration'] + datetime.timedelta(hours=1)
         data = {'group':group.pk,
                 'meeting_type':'single',
                 'session_set-0-id':meeting.session_set.first().id,
                 'session_set-0-date':formset_initial['date'].strftime('%Y-%m-%d'),
                 'session_set-0-time':new_time.strftime('%H:%M'),
-                'session_set-0-requested_duration':formset_initial['requested_duration'],
+                'session_set-0-requested_duration':self.strfdelta(new_duration, '{hours}:{minutes}'),
                 'session_set-0-remote_instructions':formset_initial['remote_instructions'],
                 #'session_set-0-agenda':formset_initial['agenda'],
                 'session_set-0-agenda_note':formset_initial['agenda_note'],
@@ -1299,7 +1300,14 @@ class InterimTests(TestCase):
         session = meeting.session_set.first()
         timeslot = session.official_timeslotassignment().timeslot
         self.assertEqual(timeslot.time,new_time)
-        
+        self.assertEqual(timeslot.duration,new_duration)
+    
+    def strfdelta(self, tdelta, fmt):
+        d = {"days": tdelta.days}
+        d["hours"], rem = divmod(tdelta.seconds, 3600)
+        d["minutes"], d["seconds"] = divmod(rem, 60)
+        return fmt.format(**d)
+
     def test_interim_request_details_permissions(self):
         make_meeting_test_data()
         meeting = Meeting.objects.filter(type='interim',session__status='apprw',session__group__acronym='mars').first()