diff --git a/netbox/dcim/forms.py b/netbox/dcim/forms.py
index 3c515152e..902541353 100644
--- a/netbox/dcim/forms.py
+++ b/netbox/dcim/forms.py
@@ -75,7 +75,7 @@ class InterfaceCommonForm:
             self.cleaned_data['tagged_vlans'] = []
 
         # Validate tagged VLANs; must be a global VLAN or in the same site
-        else:
+        elif self.cleaned_data['mode'] == IFACE_MODE_TAGGED:
             valid_sites = [None, self.cleaned_data['device'].site]
             invalid_vlans = [str(v) for v in tagged_vlans if v.site not in valid_sites]