diff --git a/awx/api/serializers.py b/awx/api/serializers.py
index 060ce1cb91..3639efdf2b 100644
--- a/awx/api/serializers.py
+++ b/awx/api/serializers.py
@@ -2272,7 +2272,7 @@ class InventorySourceSerializer(UnifiedJobTemplateSerializer, InventorySourceOpt
         if get_field_from_model_or_attrs('source') == 'scm':
             if ('source' in attrs or 'source_project' in attrs) and get_field_from_model_or_attrs('source_project') is None:
                 raise serializers.ValidationError({"source_project": _("Project required for scm type sources.")})
-        elif get_field_from_model_or_attrs('source') == 'constructed':
+        elif (get_field_from_model_or_attrs('source') == 'constructed') and (self.instance and self.instance.source != 'constructed'):
             raise serializers.ValidationError({"Error": _('constructed not a valid source for inventory')})
         else:
             redundant_scm_fields = list(filter(lambda x: attrs.get(x, None), ['source_project', 'source_path']))