diff --git a/nixos/modules/services/networking/openconnect.nix b/nixos/modules/services/networking/openconnect.nix
index 5a02bd072257..7f9006053b89 100644
--- a/nixos/modules/services/networking/openconnect.nix
+++ b/nixos/modules/services/networking/openconnect.nix
@@ -90,6 +90,7 @@ let
   generateConfig = name: icfg:
     pkgs.writeText "config" ''
       interface=${name}
+      ${optionalString (icfg.protocol != null) "protocol=${icfg.protocol}"}
       ${optionalString (icfg.user != null) "user=${icfg.user}"}
       ${optionalString (icfg.passwordFile != null) "passwd-on-stdin"}
       ${optionalString (icfg.certificate != null)