diff --git a/docs/caching.md b/docs/caching.md
index 7cbf660d..143218e1 100644
--- a/docs/caching.md
+++ b/docs/caching.md
@@ -11,6 +11,10 @@ The cache is backed by [SPTPersistentCache](https://github.com/spotify/SPTPersis
 The caching is based on the url of the asset.
 SPTPersistentCache is a LRU ([last recently used](https://en.wikipedia.org/wiki/Cache_replacement_policies#Least_recently_used_(LRU))) cache.
 
+# Restrictions
+
+Currenly the uri of the resource that should be cached needs to have the appropriate file extension (one of `mp4`, `m4v` or `mov`). In order to be cached. In future versions (once dependencies allow access to the `content-type` header) this will no longer be necessary. You will also receive warnings in the xcode logs by using the `debug` mode. So if you are not 100% sure if your video is cached, check your xcode logs!
+
 By default files expire after 30 days and the maxmimum cache size is 100mb.
 
 In a future release the cache might have more configurable options.