diff --git a/nixos/modules/services/networking/ddclient.nix b/nixos/modules/services/networking/ddclient.nix
index fd9c216b0602..8a2c0fc7080c 100644
--- a/nixos/modules/services/networking/ddclient.nix
+++ b/nixos/modules/services/networking/ddclient.nix
@@ -31,8 +31,8 @@ let
   preStart = ''
     install ${configFile} /run/${RuntimeDirectory}/ddclient.conf
     ${lib.optionalString (cfg.configFile == null) (if (cfg.passwordFile != null) then ''
-      password=$(head -n 1 ${cfg.passwordFile})
-      sed -i "s/^password=$/password=$password/" /run/${RuntimeDirectory}/ddclient.conf
+      password=$(printf "%q" "$(head -n 1 "${cfg.passwordFile}")")
+      sed -i "s|^password=$|password=$password|" /run/${RuntimeDirectory}/ddclient.conf
     '' else ''
       sed -i '/^password=$/d' /run/${RuntimeDirectory}/ddclient.conf
     '')}