diff --git a/README.md b/README.md
index 4bfbdb5..67eca41 100644
--- a/README.md
+++ b/README.md
@@ -427,8 +427,10 @@ MellonDiagnosticsEnable Off
         # Default: None set.
         MellonSPMetadataFile /etc/apache2/mellon/sp-metadata.xml
 
-        # If you choose to autogenerate metadata, this option
-        # can be used to control the SP entityId
+        # This option can be used to explicitly set the entityID Mellon
+        # will present itself as, in authentication and autogenerated metadata.
+        # If no entityID is supplied via MellonSPMetadataFile or MellonSPentityID,
+        # it will be set to Mellon's metadata URL (https://<yourhost>/mellon/metadata).
         # MellonSPentityId "https://www.example.net/foo"
         #
         # If you choose to autogenerate metadata, these options