diff --git a/tox.ini b/tox.ini
index 239f123b..326b9b42 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,8 +8,8 @@ stxdir = {toxinidir}/..
 # defaulted here to the path that works in developer environments
 [testenv]
 install_command = pip install \
-    -v -v -v \
-    -c https://opendev.org/openstack/requirements/raw/branch/stable/stein/upper-constraints.txt  \
+    -v -v -v --use-deprecated legacy-resolver \
+    -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/stable/stein/upper-constraints.txt} \
     {opts} {packages}
 
 setenv = VIRTUAL_ENV={envdir}