diff --git a/README.md b/README.md
index c1a868e..84f4c4c 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,12 @@
 # wmclient - WURFL Microservice Client for Python
 
+## Differences between version 2.2.0 and previous ones.
+
+Version 2.2.0 makes WURFL microservice client backward compatible with Python 2.7. To do that it replaces two libraries that are available for Python 3.x only:
+
+- pywurfl (replaced by urrllib3)
+- @lru_cache (replaced by pylru)
+
 ## Python WURFL Microservice Client
 
 WURFL Microservice (by ScientiaMobile, Inc.) is a mobile device detection service that can quickly and accurately detect over 500 capabilities of visiting devices. It can differentiate between portable mobile devices, desktop devices, SmartTVs and any other types of devices that have a web browser.