diff --git a/doc/postgis.xml b/doc/postgis.xml
index cc39c93bc..77a27a0fd 100644
--- a/doc/postgis.xml
+++ b/doc/postgis.xml
@@ -3587,6 +3587,17 @@ dimension
           </listitem>
         </varlistentry>
 
+        <varlistentry id="zmflag">
+          <term>zmflag(geometry)</term>
+
+          <listitem>
+            <para>Returns ZM (dimension semantic) flag of the geometries as
+	    a small int. Values are: 0=2d, 1=3dm, 2=3dz, 3=4d.
+	    </para>
+          </listitem>
+        </varlistentry>
+
+
         <varlistentry>
           <term>length2d(geometry)</term>