diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index 22c1e8ed47..171b8df8f3 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -3220,6 +3220,24 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-RM_OLD_IMAGE'><glossterm>RM_OLD_IMAGE</glossterm>
+            <glossdef>
+                <para>
+                    Reclaims disk space by removing previously built
+                    versions of the same image from the
+                    <filename>images</filename> directory pointed to by the
+                    <link linkend='var-DEPLOY_DIR'><filename>DEPLOY_DIR</filename></link>
+                    variable.
+                </para>
+
+                <para>
+                    Set this variable to "1" in your
+                    <filename>local.conf</filename> file to remove these
+                    images.
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-RM_WORK_EXCLUDE'><glossterm>RM_WORK_EXCLUDE</glossterm>
             <glossdef>
                 <para>