diff --git a/submissions/admin.py b/submissions/admin.py
index d41460b4eabb23170af755deec166f5c64f55389..6fb310504c3b30953696f87c9a1c38d4f2937357 100644
--- a/submissions/admin.py
+++ b/submissions/admin.py
@@ -32,6 +32,7 @@ class SubmissionAdminForm(forms.ModelForm):
         required=False,
         queryset=Contributor.objects.order_by('user__last_name'))
     is_resubmission_of = forms.ModelChoiceField(
+        required=False,
         queryset=Submission.objects.order_by('-preprint__identifier_w_vn_nr'))
 
     class Meta: