diff --git a/docs/contributing.rst b/docs/contributing.rst
index 74f43e2f..b9a077d6 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -29,6 +29,8 @@ The next step is to create a virtual environment for your project and use it to
     cd datasette
     # Create a virtual environment in venv/
     python3 -mvenv venv
+    # Now activate the virtual environment, so pip can install into it
+    source venv/bin/activate
     # Install Datasette and its testing dependencies
     pip install -e .[test]