diff --git a/nixos/modules/services/misc/autofs.nix b/nixos/modules/services/misc/autofs.nix
index 5e7c1e668288..541f0d2db19f 100644
--- a/nixos/modules/services/misc/autofs.nix
+++ b/nixos/modules/services/misc/autofs.nix
@@ -52,6 +52,7 @@ in
       };
 
       timeout = mkOption {
+        type = types.int;
         default = 600;
         description = "Set the global minimum timeout, in seconds, until directories are unmounted";
       };