diff --git a/applications/NXmx.nxdl.xml b/applications/NXmx.nxdl.xml
index 55cfe520cb..7debc35c0c 100644
--- a/applications/NXmx.nxdl.xml
+++ b/applications/NXmx.nxdl.xml
@@ -422,6 +422,15 @@
 
 							If the full bit depths is not required, providing a
 							mask with fewer bits is permissible.
+
+							If needed, additional pixel masks can be specified by
+							including addtional entries named pixel_mask_N, where
+							N is an integer. For example, a general bad pixel mask
+							could be specified in pixel_mask that indicates noisy
+							and dead pixels, and an additional pixel mask from
+							experiment-specific shadowing could be specified in
+							pixel_mask_2. The cummulative mask is the bitwise OR
+							of pixel_mask and any pixel_mask_N entries.
 						</doc>
 						<dimensions rank="dataRank">
 							<dim index="1" value="i" />
@@ -429,18 +438,6 @@
 							<dim index="3" value="k" required="false"/>
 						</dimensions>
 					</field>
-					<field name="dynamic_mask" type="NX_INT" >
-						<doc>
-							Additional 32-bit pixel mask for the detector, useful if a second set
-							of masks needs to be combined with pixel_mask.  Dimensionality and
-							bit values are as defined for pixel_mask.
-						</doc>
-						<dimensions rank="dataRank">
-							<dim index="1" value="i"/>
-							<dim index="2" value="j"/>
-							<dim index="3" value="k" required="false"/>
-						</dimensions>
-					</field>
 					<field name="countrate_correction_applied" type="NX_BOOLEAN"
 						minOccurs="0">
 						<doc>
diff --git a/base_classes/NXdetector.nxdl.xml b/base_classes/NXdetector.nxdl.xml
index 75267a982d..e1760a275d 100644
--- a/base_classes/NXdetector.nxdl.xml
+++ b/base_classes/NXdetector.nxdl.xml
@@ -623,17 +623,14 @@
       If the full bit depths is not required, providing a
       mask with fewer bits is permissible.
 
-    </doc>
-    <dimensions rank="2">
-      <dim index="1" value="i"/>
-      <dim index="2" value="j"/>
-    </dimensions>
-  </field>
-  <field name="dynamic_mask" type="NX_INT" >
-    <doc>
-      Additional 32-bit pixel mask for the detector, useful if a second set
-      of masks needs to be combined with pixel_mask.  Dimensionality and
-      bit values are as defined for pixel_mask.
+      If needed, additional pixel masks can be specified by
+      including addtional entries named pixel_mask_N, where
+      N is an integer. For example, a general bad pixel mask
+      could be specified in pixel_mask that indicates noisy
+      and dead pixels, and an additional pixel mask from
+      experiment-specific shadowing could be specified in
+      pixel_mask_2. The cummulative mask is the bitwise OR
+      of pixel_mask and any pixel_mask_N entries.
     </doc>
     <dimensions rank="2">
       <dim index="1" value="i"/>