diff --git a/bolt/docs/doxygen.cfg.in b/bolt/docs/doxygen.cfg.in
--- a/bolt/docs/doxygen.cfg.in
+++ b/bolt/docs/doxygen.cfg.in
@@ -38,7 +38,7 @@
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         =
+PROJECT_NUMBER         = @PACKAGE_VERSION@
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a