diff --git a/slices/xml-core.yaml b/slices/xml-core.yaml
index b9b6ab5a3..d38ecf2ec 100644
--- a/slices/xml-core.yaml
+++ b/slices/xml-core.yaml
@@ -9,6 +9,9 @@ slices:
   #/usr/bin/dh_installxmlcatalogs:
   #/usr/sbin/update-xmlcatalog:
 
+  # this package depends officially on the 'sed' tool, but
+  # this is afaict only used by the above perl scripts that
+  # we have taken care of in this slice by the mutation script.
   catalog:
     essential:
       - sgml-base_catalog