diff --git a/README.md b/README.md
index 219eb2a..402ca68 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ this repo in one of the dev environment containers.
 
 Next, install and activate a virtualenv:
 ```sh
-sudo apt install libkrb5-dev python3-dev
+sudo apt install libkrb5-dev libsasl2-dev python3-dev
 python3 -m venv venv
 . venv/bin/activate
 pip install -r requirements.txt
diff --git a/dev-requirements.txt b/dev-requirements.txt
index 8392fb6..2a5a2f5 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -1,6 +1,7 @@
 flake8==3.9.2
 setuptools==40.8.0
 wheel==0.36.2
+cffi==1.14.6
 pytest==6.2.4
 aiosmtpd==1.4.2
 aiohttp==3.7.4.post0