diff --git a/ops/nixos/lib/blade-router.nix b/ops/nixos/lib/blade-router.nix
index 0c2ed7e545..61d5605149 100644
--- a/ops/nixos/lib/blade-router.nix
+++ b/ops/nixos/lib/blade-router.nix
@@ -6,6 +6,8 @@
 with lib;
 let
   notifyBird = pkgs.writeScript "blade-router-vrrp-bird.sh" ''
+    #!${pkgs.runtimeShell}
+
     ENDSTATE=$3
     NAME=$2
     TYPE=$1