diff --git a/pkgs/development/ruby-modules/gem-config/default.nix b/pkgs/development/ruby-modules/gem-config/default.nix
index d5595c04e3a2..987d61f2e336 100644
--- a/pkgs/development/ruby-modules/gem-config/default.nix
+++ b/pkgs/development/ruby-modules/gem-config/default.nix
@@ -21,11 +21,20 @@
 , libiconv, postgresql, v8_3_16_14, clang, sqlite, zlib, imagemagick
 , pkgconfig , ncurses, xapian_1_2_22, gpgme, utillinux, fetchpatch, tzdata, icu, libffi
 , cmake, libssh2, openssl, mysql, darwin, git, perl, gecode_3, curl
-, libmsgpack, qt48, libsodium, snappy, libossp_uuid, lxc, libpcap
+, libmsgpack, qt48, libsodium, snappy, libossp_uuid, lxc, libpcap, buildRubyGem
 }@args:
 
 let
   v8 = v8_3_16_14;
+
+  rainbow_rake = buildRubyGem {
+    name = "rake";
+    gemName = "rake";
+    remotes = ["https://rubygems.org"];
+    sha256 = "01j8fc9bqjnrsxbppncai05h43315vmz9fwg28qdsgcjw9ck1d7n";
+    type = "gem";
+    version = "12.0.0";
+  };
 in
 
 {
@@ -149,6 +158,10 @@ in
     buildInputs = [ openssl ];
   };
 
+  rainbow = attrs: {
+    buildInputs = [ rainbow_rake ];
+  };
+
   rbnacl = spec: {
     postInstall = ''
     sed -i $(cat $out/nix-support/gem-meta/install-path)/lib/rbnacl.rb -e "2a \