diff --git a/lib/zlib/deflate.js b/lib/zlib/deflate.js
index 7e0754f..edd21c9 100644
--- a/lib/zlib/deflate.js
+++ b/lib/zlib/deflate.js
@@ -168,6 +168,9 @@ function fill_window(s) {
        later. (Using level 0 permanently is not an optimal usage of
        zlib, so we don't care about this pathological case.)
        */
+
+      // TODO: check if shortlinks to `s.head` & `s.prev` improve speed.
+
       n = s.hash_size;
       p = n;
       do {