diff --git a/noxfile.py b/noxfile.py
index adce2527c..7bc1af24d 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -92,8 +92,8 @@ def unit(session):
 
 @nox.session(python=["2.7"])
 def unit_prev_versions(session):
-    session.install(*TEST_DEPENDENCIES)
     session.install(".")
+    session.install(*TEST_DEPENDENCIES)
     session.run(
         "pytest", "--cov=google.auth", "--cov=google.oauth2", "--cov=tests", "tests"
     )