diff --git a/documentation/dev-manual/dev-manual-common-tasks.xml b/documentation/dev-manual/dev-manual-common-tasks.xml
index 5694776b88..f45e19fb95 100644
--- a/documentation/dev-manual/dev-manual-common-tasks.xml
+++ b/documentation/dev-manual/dev-manual-common-tasks.xml
@@ -4558,9 +4558,17 @@
                             option or the equivalent rootfs derived from the
 			                <filename>-e</filename> command-line
 			                option.
-                            Exactly what those contents and
-			                filesystem type end up being are dependent
-			                on the given plugin implementation.
+                            Exactly what those contents and filesystem type end
+                            up being are dependent on the given plugin
+                            implementation.
+                            </para>
+                            <para>If you do not use the
+                            <filename>--source</filename> option, the
+                            <filename>wic</filename> command creates an empty
+                            partition.
+                            Consequently, you must use the
+                            <filename>--size</filename> option to specify the
+                            size of the empty partition.
                             </para></listitem>
                         <listitem><para><emphasis><filename>--ondisk</filename> or <filename>--ondrive</filename>:</emphasis>
                             Forces the partition to be created on a particular