diff --git a/lib/storage/file.js b/lib/storage/file.js
index 7c0a773cc..bc0830d4e 100644
--- a/lib/storage/file.js
+++ b/lib/storage/file.js
@@ -682,7 +682,7 @@ export type ChainPadServer_ChannelInternal_t = {
 var getChannel = function (
     env,
     id,
-    callback /*:(err:?Error, chan:?ChainPadServer_ChannelInternal_t)=>void*/
+    _callback /*:(err:?Error, chan:?ChainPadServer_ChannelInternal_t)=>void*/
 ) {
     var callback = Util.once(Util.mkAsync(_callback));
     if (env.channels[id]) {