diff --git a/pyproject.toml b/pyproject.toml
index e382f89..88ed531 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -76,7 +76,7 @@ optional = true
 
 [tool.poetry.group.docs.dependencies]
 sphinx = ">=6,<8"
-sphinx-rtd-theme = ">=1.3,<3.0"
+sphinx-rtd-theme = ">=1.3,<4.0"
 expiringdict = ">=1.1.4"
 pyrfc3339 = ">=1.0"
 jsonpickle = ">1.4.1"