diff --git a/README.rst b/README.rst
index ef1970f51..8925e7c49 100644
--- a/README.rst
+++ b/README.rst
@@ -788,7 +788,7 @@ dependencies into a virtual env.
 Once this is done, you may wish to run Synapse's unit tests, to
 check that everything is installed as it should be::
 
-    PYTHONPATH="" trial tests
+    PYTHONPATH="." trial tests
 
 This should end with a 'PASSED' result::