diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 8419ab3ac..d02cca0bb 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -48,7 +48,7 @@ REQUIREMENTS = [
     "unpaddedbase64>=1.1.0",
     "canonicaljson>=1.4.0",
     # we use the type definitions added in signedjson 1.1.
-    "signedjson>=1.1.0",
+    "signedjson>=1.1.0,<=1.1.1",
     "pynacl>=1.2.1",
     "idna>=2.5",
     # validating SSL certs for IP addresses requires service_identity 18.1.