diff --git a/nixos/modules/services/mail/stalwart.nix b/nixos/modules/services/mail/stalwart.nix
index 9dfd5f2e480f..f64f334ee9d4 100644
--- a/nixos/modules/services/mail/stalwart.nix
+++ b/nixos/modules/services/mail/stalwart.nix
@@ -273,6 +273,7 @@ in
           RestrictAddressFamilies = [
             "AF_INET"
             "AF_INET6"
+            "AF_UNIX"
           ];
           RestrictNamespaces = true;
           RestrictRealtime = true;