diff --git a/Documentation/Developers/PKG-BUILD-VARS b/Documentation/Developers/PKG-BUILD-VARS
index 60ef9749a..6086e957a 100644
--- a/Documentation/Developers/PKG-BUILD-VARS
+++ b/Documentation/Developers/PKG-BUILD-VARS
@@ -6,7 +6,9 @@ config ........ Name of the active configuration ($base/config/$config/..)
 extraver ...... version text after the fist whitespace, or $rockver
 rockver ....... ROCK Linux Version (including rel. date for snapshots)
 
-pkg ........... name of the package we are building
+pkg ........... base name part of the package we are building 
+xpkg .......... derived name part of the package we are building
+                if a package is not pkgfork'd, pkg == xpkg
 ver ........... package Version (from *.desc - until first whitespace)
 desc_[A-Z] .... Data from the *.desc file