diff --git a/repos.ini b/repos.ini
index 88d629a..556bfbc 100644
--- a/repos.ini
+++ b/repos.ini
@@ -16,6 +16,13 @@
 # %(adaptation)    The device specific adaptation, for example 'n900' or 'n950-n9'
 #
 #
+# Variables may contain other variables. Resolving is done recursively from the
+# innermost variable.
+#
+# Basic variable substitution is supported:
+# %(foo:+bar) -- expands to "" if foo is set, bar otherwise
+# %(foo:-bar) -- expands to %(foo) if foo is set, bar otherwise
+#
 # Repository lookup will happen based on the 'repo' parameter in repository
 # URLs. For RnD repositories order will be <flavour> -> rnd -> all, for
 # release repositories release -> all.
diff --git a/rpm/ssu.changes b/rpm/ssu.changes
index c30bcce..1421054 100644
--- a/rpm/ssu.changes
+++ b/rpm/ssu.changes
@@ -1,3 +1,6 @@
+* Fri Mar 22 2013 Bernd Wachter <bernd.wachter@jollamobile.com> - 0.25
+- Add variable substitution
+
 * Thu Mar 21 2013 Bernd Wachter <bernd.wachter@jollamobile.com> - 0.24
 - Add support for arbitrary variables in flavour groups
 - Split off device info and settings functionality
diff --git a/rpm/ssu.spec b/rpm/ssu.spec
index 2ebffd3..ea7b6a8 100644
--- a/rpm/ssu.spec
+++ b/rpm/ssu.spec
@@ -1,5 +1,5 @@
 Name: ssu
-Version: 0.24
+Version: 0.25
 Release: 1
 Summary: SSU enabler for RND
 Group: System/Base