diff --git a/pyproject.toml b/pyproject.toml
index 8863374..f71e658 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -68,7 +68,7 @@ dev = [
 
 [tool.poetry.group.docs.dependencies]
 sphinx = ">=6.0"
-sphinx-rtd-theme = "^1.3.0"
+sphinx-rtd-theme = ">=1.3,<4.0"
 myst-parser = ">=1.0.0,<4.0.0"
 sphinx-autodoc-typehints = ">=1.24,<3.0"
 sphinx-copybutton = "^0.5.2"