diff --git a/applications/NXmx.nxdl.xml b/applications/NXmx.nxdl.xml
index 3c23badbb..02ec76cbb 100644
--- a/applications/NXmx.nxdl.xml
+++ b/applications/NXmx.nxdl.xml
@@ -635,7 +635,7 @@
                             True when count-rate correction has been applied, false otherwise.
                         </doc>
                     </field>
-                    <field name="countrate_correction_lookup_table" type="NX_NUMBER" >
+                    <field name="countrate_correction_lookup_table" type="NX_NUMBER" optional="true">
                         <doc>
                             The countrate_correction_lookup_table defines the LUT used for count-rate
                             correction. It maps a measured count :math:`c` to its corrected value