diff --git a/ippisite/ippidb/forms.py b/ippisite/ippidb/forms.py
index 206bad700420c0bd8f0e275f8a938b897f1c47ed..ab1fb55f1e1535fd3dbf96b4bcbbccfe8043f6d1 100644
--- a/ippisite/ippidb/forms.py
+++ b/ippisite/ippidb/forms.py
@@ -716,6 +716,7 @@ class TestActivityDescriptionForm(forms.ModelForm):
         queryset=Protein.objects.none(),
         label=_("protein_domain_bound_complex_label"),
         help_text=_("protein_domain_bound_complex_help_text"),
+        required=True,
     )
 
     class Meta:
@@ -792,6 +793,8 @@ class TestActivityDescriptionBaseModelFormSet(BaseInlineNestedFormSet):
         form.nested.set_compound_names(self.__compound_names)
         form.nested.set_modulation_type(self.__modulation_type)
         form.fields["protein_complex"].queryset = Protein.objects.filter(id__in=self.__protein_subset_ids)
+        if Protein.objects.filter(id__in=self.__protein_subset_ids).count() == 1:
+            form.fields["protein_complex"].initial = Protein.objects.filter(id__in=self.__protein_subset_ids).first()
 
     def set_compound_names(self, compound_names):
         """