diff --git a/samples/knot.full.conf b/samples/knot.full.conf
index a0ec438593421d180e9e2402bb947441d38005a8..cd1ec7f95e020b530a972ef0bcd3a182cc7887fd 100644
--- a/samples/knot.full.conf
+++ b/samples/knot.full.conf
@@ -119,7 +119,7 @@ zones {
   # Shared options for all listed zones
   #
 
-  # Build differences from zone file changes
+  # Build differences from zone file changes. EXPERIMENTAL feature.
   # Possible values: on|off
   # Default value: off
   ixfr-from-differences off;