diff --git a/Fastfox.js b/Fastfox.js
index fcdba58..be224f5 100644
--- a/Fastfox.js
+++ b/Fastfox.js
@@ -165,6 +165,16 @@ user_pref("content.notify.interval", 100000); // (.10s); default=120000 (.12s)
 //user_pref("browser.cache.disk.capacity", 512000); // default=256000; size of disk cache; 1024000=1GB, 2048000=2GB
 //user_pref("browser.cache.disk.max_entry_size", 51200); // DEFAULT (50 MB); maximum size of an object in disk cache
 
+// PREF: race condition of disk cache and network server
+// Firefox concurrently sends requests for cached resources to both the
+// local disk cache and the network server. The browser uses whichever
+// result arrives first and cancels the other request. This approach sometimes
+// loads pages faster because the network can be quicker than accessing the cache
+// on a hard drive. When RCWN is enabled, the request might be served from
+// the server even if you have valid entry in the cache. This will break some
+// cache related tests.
+//user_pref("network.http.rcwn.enabled", true); // DEFAULT
+
 // PREF: cache memory pool
 // Cache v2 provides a memory pool that stores metadata (such as response headers)
 // for recently read cache entries [1]. It is managed by a cache thread, and caches with