diff --git a/README.md b/README.md
index d2dc3b27608dc4b5ef3cbb33a61edb0529150a3b..1b0348b6967120907800f613d2025f7a576c3d39 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,7 @@ the prerequsites manually. The following is a list of the preequsites that need
     pynmea2 >= 1.4.2
     pyserial >= 2.7
     requests >= 2.7.0
+    cachetools >= 1.1.5
 
 The application is written for python 3 specifically, it may not work with python 2. Once installed copy the
 apex.cfg.example file over to apex.cfg in the same directory, then edit the file and replace it with your details. Next