diff --git a/tox.ini b/tox.ini
index e735c6966..6d3ee993c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -345,6 +345,7 @@ commands = bindep {posargs:test}
 # --- project requirements ----------------------------------------------------
 
 [testenv:lower-constraints]
-deps =
-    {[testenv]deps}
-    -c{toxinidir}/lower-constraints.txt
+
+setenv =
+    {[testenv]setenv}
+    TOX_CONSTRAINTS = -c{toxinidir}/lower-constraints.txt