diff --git a/README.rst b/README.rst
index 3871fa1b0..e675c3ade 100644
--- a/README.rst
+++ b/README.rst
@@ -37,7 +37,7 @@ pre-release code), you should create a virtualenv and install into that:
 
 * ``git clone https://github.com/tahoe-lafs/tahoe-lafs.git``
 * ``cd tahoe-lafs``
-* ``virtualenv venv``
+* ``virtualenv --python=python2.7 venv``
 * ``venv/bin/pip install --editable .``
 * ``venv/bin/tahoe --version``