diff --git a/pyproject.toml b/pyproject.toml
index 4dee95e..35a5a25 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,7 +18,7 @@ dependencies = [
     "myst-parser>=1,<4",
     "pre-commit>=3,<4",  # Allow us to run pre-commit hooks in testing
     "pydocstyle>=6,<7",  # Style guidelines for Python documentation
-    "sphinx>6,<8",  # The default Python documentation engine
+    "sphinx>6,<9",  # The default Python documentation engine
     "sphinx-autoapi>=3,<4",  # Generates documentation from docstrings
     "sphinx-issues>=4,<5",  # Allows references to GitHub issues
     "tox>=4,<5",  # Python test environment manager