diff --git a/apps/default.nix b/apps/default.nix
index 5adc84c..7c029f8 100644
--- a/apps/default.nix
+++ b/apps/default.nix
@@ -31,7 +31,7 @@ rec {
     program = "${drv}/bin/nova-image";
     function = attrs: bootDesc:
       nixpkgs.runCommand "nova-iso" (attrs // { inherit bootDesc; })
-      "${drv}/bin/nova-image $out $bootDesc";
+      "${drv}/bin/nova-image $bootDesc > $out";
   };
 
   nova-iso = let
@@ -44,7 +44,7 @@ rec {
     program = "${drv}/bin/nova-iso";
     function = attrs: bootDesc:
       nixpkgs.runCommand "nova.iso" attrs
-      ''${drv}/bin/nova-iso $out "${bootDesc}"'';
+      ''${drv}/bin/nova-iso "${bootDesc}" > $out'';
   };
 
   render-init =
diff --git a/apps/nova-iso/default.nix b/apps/nova-iso/default.nix
index 7f159f0..21d9478 100644
--- a/apps/nova-iso/default.nix
+++ b/apps/nova-iso/default.nix
@@ -9,14 +9,6 @@ nixpkgs.writeScriptBin "nova-iso" (with nixpkgs.buildPackages;
     #!${runtimeShell}
     set -eu
 
-    out="$1"
-    shift
-
-    if [ -e "$out" ]; then
-      echo "refusing to overwrite $out as output" > /dev/stderr
-      exit 1
-    fi
-
     SYSLINUX="${syslinux}/share/syslinux"
 
     TMPDIR="$(${coreutils}/bin/mktemp -d)"
@@ -25,7 +17,8 @@ nixpkgs.writeScriptBin "nova-iso" (with nixpkgs.buildPackages;
     mkdir -p "$TMPDIR/boot/syslinux"
     ${nova-image.program} "$TMPDIR/boot/image.elf" $@
 
-    pushd "$TMPDIR"
+    pushd "$TMPDIR" > /dev/null
+    out="nova.iso"
 
     # build ISO layout
     cp ${packages.NOVA}/hypervisor* boot/hypervisor
@@ -46,5 +39,5 @@ nixpkgs.writeScriptBin "nova-iso" (with nixpkgs.buildPackages;
     	boot
 
     ${syslinux}/bin/isohybrid "$out"
-    echo ISO is at $out
+    cat "$out"
   '')