diff --git a/README.md b/README.md
index e676d27..eef17e9 100644
--- a/README.md
+++ b/README.md
@@ -32,7 +32,7 @@ For this guide we'll use ptlib 2.18.6 and opal 3.18.6.
 #### Installing Requirements
 First we'll need some packages
 ```bash
-apt-get install build-essential git wget pkg-config libssl-dev libsrtp2-dev -y
+apt-get install build-essential git wget pkg-config libssl-dev libsrtp2-dev libspandsp-dev -y
 ```
 #### Download sourcecode
 Versions:
@@ -263,6 +263,9 @@ sudo chmod 700 /etc/t38modem/config
 - Pitfalls:
   - If you are already connected to your SIP server it may not give proper response codes. My provider returns `500 Internal Server Error`
   - Test the command before running the init script!
+  - Do not try to used `ATO` to switch to a data connection, t38modem will return `ERROR`.
+  Thats hardcoded in `pmodeme.cxx` in `void ModemEngineBody::HandleCmdRest(PString &resp)`.
+  Dont let that hodld you back.
 
 ### systemd service
 If you want to run a fax server, you can create a systemd service to let your emulated fax modem start automatically on system boot.