diff --git a/tox.ini b/tox.ini
index 07e3172c8..d3ca8eb63 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,7 @@ skipsdist = True
 stxdir = {toxinidir}/..
 
 [testenv]
-install_command = pip install -U \
+install_command = pip install --use-deprecated legacy-resolver -U \
   -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/stable/stein/upper-constraints.txt} \
   {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}