diff --git a/doc/manuals/osmopcu-usermanual.adoc b/doc/manuals/osmopcu-usermanual.adoc
index 5d2b09c..f47a0a9 100644
--- a/doc/manuals/osmopcu-usermanual.adoc
+++ b/doc/manuals/osmopcu-usermanual.adoc
@@ -1,3 +1,5 @@
+:gfdl-enabled:
+
 OsmoPCU User Manual
 ===================
 Harald Welte <hwelte@sysmocom.de>
