diff --git a/requirements-dev.txt b/requirements-dev.txt
index 2194b464..c87e6359 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,7 +1,6 @@
 -r requirements.txt
 -r requirements-test.txt
-tox==4.55.1 ; python_version >= "3.10"
-tox==4.55.1 ; python_version < "3.10"
+tox==4.56.1
 wheel==0.47.0
 Sphinx==9.0.4 ; python_version >= "3.11"
 Sphinx==7.4.7 ; python_version < "3.11"
diff --git a/tox.ini b/tox.ini
index 8d3f39cf..c4a0608c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,4 +1,8 @@
 [tox]
+# tox 4.56.0 changed the default of skip_missing_interpreters back to false
+# (https://github.com/tox-dev/tox/pull/3966). CI runners install only one
+# Python version per job, so missing interpreters must be skipped, not failed.
+skip_missing_interpreters = true
 envlist =
     py3.10,
     py3.11,