diff --git a/nixos/modules/services/networking/shairport-sync.nix b/nixos/modules/services/networking/shairport-sync.nix
index b4b86a2d55be..ac526c0e9f6f 100644
--- a/nixos/modules/services/networking/shairport-sync.nix
+++ b/nixos/modules/services/networking/shairport-sync.nix
@@ -28,6 +28,7 @@ in
       };
 
       arguments = mkOption {
+        type = types.str;
         default = "-v -o pa";
         description = ''
           Arguments to pass to the daemon. Defaults to a local pulseaudio
@@ -36,6 +37,7 @@ in
       };
 
       user = mkOption {
+        type = types.str;
         default = "shairport";
         description = ''
           User account name under which to run shairport-sync. The account