diff --git a/base_classes/NXbeam.nxdl.xml b/base_classes/NXbeam.nxdl.xml
index 95eec3f60..1c258152f 100644
--- a/base_classes/NXbeam.nxdl.xml
+++ b/base_classes/NXbeam.nxdl.xml
@@ -334,6 +334,7 @@
         </dimensions>
     </field>
     <field name="chirp_type" type="NX_CHAR">
+        <!-- REVISIT: should this be an open enumeration? -->
         <doc>
              The type of chirp implemented
         </doc>