diff --git a/examples/recovery.nix b/examples/recovery.nix
index 535306e..55b6efe 100644
--- a/examples/recovery.nix
+++ b/examples/recovery.nix
@@ -31,6 +31,7 @@ in rec {
   boot.tftp = {
     ipaddr = "10.0.0.8"; # my address
     serverip = "10.0.0.1"; # build machine or other tftp server
+    freeSpaceBytes = 1024 * 1024 * 4;
   };
 
   hostname = "recovery";
diff --git a/modules/outputs/tftpboot.nix b/modules/outputs/tftpboot.nix
index ad6ed63..274ebad 100644
--- a/modules/outputs/tftpboot.nix
+++ b/modules/outputs/tftpboot.nix
@@ -72,6 +72,7 @@ in {
             hex() { printf "0x%x" $1; }
             rootfsStart=${toString cfg.loadAddress}
             rootfsSize=$(binsize64k ${o.rootfs} )
+            rootfsSize=$(($rootfsSize + ${toString cfg.freeSpaceBytes} ))
             dtbStart=$(($rootfsStart + $rootfsSize))
             dtbSize=$(binsize ${o.dtb} )
             imageStart=$(($dtbStart + $dtbSize))