diff --git a/nixos/modules/services/databases/foundationdb.nix b/nixos/modules/services/databases/foundationdb.nix
index 5cce94ac6d5e..c05bfc47bb77 100644
--- a/nixos/modules/services/databases/foundationdb.nix
+++ b/nixos/modules/services/databases/foundationdb.nix
@@ -94,7 +94,7 @@ in
     };
 
     listenPortStart = lib.mkOption {
-      type = lib.types.int;
+      type = lib.types.port;
       default = 4500;
       description = ''
         Starting port number for database listening sockets. Every FDB process binds to a