diff --git a/module_build_service/resolver/DBResolver.py b/module_build_service/resolver/DBResolver.py
index b191450d..f10fa6d1 100644
--- a/module_build_service/resolver/DBResolver.py
+++ b/module_build_service/resolver/DBResolver.py
@@ -324,11 +324,14 @@ class DBResolver(GenericResolver):
 
             koji_tag = build.koji_tag
             if side_tag and br_name in self.config.base_module_names:
-                # see base module has a side tag_configuration
+                # see if base module has a side tag configuration
                 side_tag_format = build.mmd().get_xmd().get("mbs", {}).get("koji_side_tag_format")
                 if side_tag_format:
                     koji_tag = side_tag_format.format(side_tag=side_tag)
                     log.info("Using side tag for base module %s: %s", br_name, koji_tag)
+                else:
+                    log.warning("Side tag requested, but base module %s lacks koji_side_tag_format"
+                                " value", br_name)
 
             # If the buildrequire is a meta-data only module with no Koji tag set, then just
             # skip it