diff --git a/core/nginx/letsencrypt.py b/core/nginx/letsencrypt.py
index 3fe8ea92..ed106fa1 100755
--- a/core/nginx/letsencrypt.py
+++ b/core/nginx/letsencrypt.py
@@ -14,7 +14,7 @@ command = [
     "--cert-name", "mailu",
     "--preferred-challenges", "http", "--http-01-port", "8008",
     "--keep-until-expiring",
-    "--rsa-key-size", "4096",
+    "--rsa-key-size", "3072",
     "--config-dir", "/certs/letsencrypt",
     "--post-hook", "/config.py"
 ]