diff --git a/lib/isc/rbtgen.c b/lib/isc/rbtgen.c
index 562811eb12..b5059ccd5d 100644
--- a/lib/isc/rbtgen.c
+++ b/lib/isc/rbtgen.c
@@ -1,4 +1,9 @@
 
+/*
+ * This file is a generic template that can be used to create a red-black
+ * tree library for a specified node type.
+ */
+
 /*
  * Red-Black Tree algorithms adapted from:
  *