diff --git a/README.rst b/README.rst
index 275e173..2c38603 100644
--- a/README.rst
+++ b/README.rst
@@ -79,7 +79,7 @@ Before installing, ensure you have:
 
 On Debian or Ubuntu, install these files with::
 
-    apt-get install build-essential python-dev libnetfilter-queue-dev
+    apt-get install build-essential python-dev-is-python3 libnetfilter-queue-dev
 
 From PyPI
 ---------