diff --git a/pyproject.toml b/pyproject.toml
index f7dd6b0a..476388c0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -71,7 +71,7 @@ optional-dependencies.dev = [
     "sphinx-copybutton==0.5.2",
     "sphinx-lint==1.0.0",
     "sphinx-pyproject==0.3.0",
-    "sphinx-substitution-extensions==2025.4.3",
+    "sphinx-substitution-extensions==2025.6.6",
     "sphinxcontrib-spelling==8.0.1",
     "sybil==9.1.0",
     "types-requests==2.32.0.20250602",