diff --git a/scipost_django/submissions/forms/__init__.py b/scipost_django/submissions/forms/__init__.py
index 8021a379f30579e557a9b824c8d7c5aa8cb680e1..c23dae5f48f9fe5ecf34cfc5f00ca628e71fc527 100644
--- a/scipost_django/submissions/forms/__init__.py
+++ b/scipost_django/submissions/forms/__init__.py
@@ -1620,7 +1620,10 @@ class SubmissionForm(forms.ModelForm):
         at least one of the authors in the list is an expected author of the collection.
         """
         # Check if no collection is selected or fetch the object
-        collection_id = self.cleaned_data.get("collection", "")
+        collection_id = self.cleaned_data.get("collection", None)
+        if collection_id is None:
+            return
+
         collection = get_object_or_404(Collection, id=collection_id)
 
         # Check that the collection is part of a series in the target journal