diff --git a/pkgs/development/web/iojs/default.nix b/pkgs/development/web/iojs/default.nix
index c0518921383..45586c1e9bd 100644
--- a/pkgs/development/web/iojs/default.nix
+++ b/pkgs/development/web/iojs/default.nix
@@ -1,7 +1,7 @@
 { stdenv, fetchurl, python, utillinux, openssl, http-parser, zlib, libuv, nightly ? false }:
 
 let
-  version = if nightly then "1.5.2-nightly201503173c8ae2d934" else "1.5.1";
+  version = if nightly then "1.6.5-nightly20150409ff74931107" else "1.6.4";
   inherit (stdenv.lib) optional maintainers licenses platforms;
 in stdenv.mkDerivation {
   name = "iojs-${version}";
@@ -11,8 +11,8 @@ in stdenv.mkDerivation {
           then "https://iojs.org/download/nightly/v${version}/iojs-v${version}.tar.gz"
           else "https://iojs.org/dist/v${version}/iojs-v${version}.tar.gz";
     sha256 = if nightly
-             then "10blf1hr80fknrzyrbj7qy2xn7wilnyn6y2r7ijrw2gns4ia3d0h"
-             else "0zdxdb9n0yk6dp6j6x3bka7vrnf7kz8jjcpl6fw5fr9f742s9s26";
+             then "04f7r4iv8p0jfylw4sxg3vsv14rbsi6n9hbqnwvdh6554yrm6d35"
+             else "1qzvf7g457dppzxn23wppjcm09vh1n6bhsvz5szhwgjvl0iv2pc7";
   };
 
   prePatch = ''
diff --git a/pkgs/development/web/iojs/update-iojs b/pkgs/development/web/iojs/update-iojs
index 3140c5e842b..4e01ecfd63e 100755
--- a/pkgs/development/web/iojs/update-iojs
+++ b/pkgs/development/web/iojs/update-iojs
@@ -3,6 +3,8 @@
 # Fetch the latest io.js release (stable/nightly) and update
 # `default.nix` in this directory.
 #
+# Call this from the root of your nixpkgs directory.
+#
 
 set -e
 
@@ -21,12 +23,13 @@ latest_log() {
 }
 
 url() {
-    nix-instantiate -A "$1" 2> /dev/null | xargs cat \
+    nix-instantiate -A "$1" \
+        | xargs cat \
         | sed 's/.*"urls","//;s/".*//'
 }
 
 hash() {
-    nix-prefetch-url "$1" 2> /dev/null
+    nix-prefetch-url "$1"
 }
 
 hash_log() {