diff --git a/tox.ini b/tox.ini
index e52b28949..27ca58bfb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -14,7 +14,7 @@ passenv =
   ZUUL_CACHE_DIR
   REQUIREMENTS_PIP_LOCATION
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2026.1}
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
 commands =
@@ -39,7 +39,7 @@ commands =
 
 [testenv:venv]
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2026.1}
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
@@ -49,7 +49,7 @@ commands = {posargs}
 description =
   Build documentation in HTML format.
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2026.1}
   -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf doc/build/html doc/build/doctrees
@@ -70,7 +70,7 @@ commands =
 description =
   Build release notes.
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2026.1}
   -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html