diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 35933324a4..0a6043ae8d 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -34,7 +34,7 @@ REQUIREMENTS = {
     "pydenticon": ["pydenticon"],
     "ujson": ["ujson"],
     "blist": ["blist"],
-    "pysaml2": ["saml2"],
+    "pysaml2>=3.0.0,<4.0.0": ["saml2>=3.0.0,<4.0.0"],
     "pymacaroons-pynacl": ["pymacaroons"],
 }
 CONDITIONAL_REQUIREMENTS = {