diff --git a/pkgs/servers/matrix-synapse/default.nix b/pkgs/servers/matrix-synapse/default.nix
index 36a967220602..6d4b18ae8772 100644
--- a/pkgs/servers/matrix-synapse/default.nix
+++ b/pkgs/servers/matrix-synapse/default.nix
@@ -65,6 +65,7 @@ buildPythonApplication rec {
     psycopg2
     pyasn1
     pydantic
+    PyICU
     pyjwt
     pymacaroons
     pynacl