diff --git a/pyproject.toml b/pyproject.toml
index 995c00c..4e69b20 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -53,7 +53,7 @@ testing-no-myst = [
 
 theme-furo = ["furo~=2024.7.18"]
 theme-pydata = ["pydata-sphinx-theme~=0.15.2"]
-theme-rtd = ["sphinx-rtd-theme~=2.0"]
+theme-rtd = ["sphinx-rtd-theme>=2,<4"]
 theme-sbt = ["sphinx-book-theme~=1.1"]
 theme-im = ["sphinx-immaterial~=0.12.2"]