diff --git a/bigquery/nox.py b/bigquery/nox.py
index b0271c954e0e..2d5772882fbe 100644
--- a/bigquery/nox.py
+++ b/bigquery/nox.py
@@ -76,7 +76,7 @@ def system_tests(session, python_version):
         os.path.join('..', 'storage'),
         os.path.join('..', 'test_utils'),
     )
-    session.install('.')
+    session.install('-e', '.')
 
     # Run py.test against the system tests.
     session.run(
@@ -109,7 +109,7 @@ def snippets_tests(session, python_version):
         os.path.join('..', 'storage'),
         os.path.join('..', 'test_utils'),
     )
-    session.install('.')
+    session.install('-e', '.')
 
     # Run py.test against the system tests.
     session.run(