diff --git a/pyproject.toml b/pyproject.toml
index b04a8855..12a0b310 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,6 +34,8 @@ dev = [
     "mkdocs>=1.6.0",
     "mkdocs-material>=9.5.47",
     "mkdocstrings[python]>=0.18",
+    # mkdocstrings<1.0.7 (the newest release that supports Python 3.10) breaks with pymdown-extensions>=12.2.
+    "pymdown-extensions<12.2; python_version < '3.11'",
     "ruff>=0.8",
     "mike>=2.1.3",
     "mkdocs-mermaid2-plugin>=1.2.3",