diff --git a/scipost/forms.py b/scipost/forms.py
index 6e86d1d46c6c7237b630e0a168b1be68dd5b9a71..172bedcc7df38bcd9fd15e31c67ce1dce0cdb117 100644
--- a/scipost/forms.py
+++ b/scipost/forms.py
@@ -67,9 +67,11 @@ class RegistrationInvitationForm(forms.ModelForm):
             {'placeholder': 'NOTE: a personal phrase or two. The bulk of the text will be auto-generated.'})
         self.fields['cited_in_submission'] = forms.ModelChoiceField(
             queryset=Submission.objects.all().exclude(
-                status__in=SUBMISSION_STATUS_PUBLICLY_UNLISTED).order_by('-submission_date'))
+                status__in=SUBMISSION_STATUS_PUBLICLY_UNLISTED).order_by('-submission_date'),
+            required=False)
         self.fields['cited_in_publication'] = forms.ModelChoiceField(
-            queryset=Publication.objects.all().order_by('-publication_date'))
+            queryset=Publication.objects.all().order_by('-publication_date'),
+            required=False)
         self.helper = FormHelper()
         self.helper.layout = Layout(
             Div(
diff --git a/scipost/views.py b/scipost/views.py
index e56bf12b0fcf1155877c99459fdd8bc7067ef82a..81425908c623e2cfa6622ee7ae49ef2aa67b5e8d 100644
--- a/scipost/views.py
+++ b/scipost/views.py
@@ -465,6 +465,9 @@ def registration_invitations(request):
                 Utils.create_invitation()
                 Utils.send_registration_invitation_email()
                 return HttpResponseRedirect('registration_invitation_sent')
+        else:
+            errormessage = 'The form was not filled validly.'
+            
     else:
         reg_inv_form = RegistrationInvitationForm()