diff --git a/lib/bcoin/chaindb.js b/lib/bcoin/chaindb.js
index 695e7a81..5751da29 100644
--- a/lib/bcoin/chaindb.js
+++ b/lib/bcoin/chaindb.js
@@ -18,6 +18,7 @@
  *   u/[hash] -> undo coins
  *   T/[address]/[hash] -> dummy (tx by address)
  *   C/[address]/[hash] -> dummy (coin by address)
+ *   q/[height] -> block hash to be pruned
  */
 
 var bcoin = require('./env');