diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index 34083ac1ba..976bf0e4bb 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -2000,7 +2000,8 @@ Core layer for images cannot be removed
         <glossentry id='var-IMAGE_ROOTFS'><glossterm>IMAGE_ROOTFS</glossterm>
             <glossdef>
                 <para>
-                    The location of the root filesystem.
+                    The location of the root filesystem while it is under
+                    construction (i.e. during <filename>do_rootfs</filename>).
                     This variable is not configurable.
                     Do not change it.
                 </para>