diff --git a/src/rex.action/setup.py b/src/rex.action/setup.py
index 1df2a3ac0..d3b13ba60 100644
--- a/src/rex.action/setup.py
+++ b/src/rex.action/setup.py
@@ -26,6 +26,7 @@
         'werkzeug>=0.10.4,<0.11',
         'inflect>=0.2.5,<0.3',
         'docutils>=0.12,<0.13',
+        'protobuf==3.20.1',
     ],
     rex_init='rex.action',
     rex_static='static',