diff --git a/README-DEV.md b/README-DEV.md
index da2025a..366f436 100644
--- a/README-DEV.md
+++ b/README-DEV.md
@@ -4,6 +4,7 @@ In a Python 3 virtualenv:
 
 ~~~
 pip install -e .
+pip install -r requirements-test.txt
 make test
 ~~~