diff --git a/pkgs/development/interpreters/ruby/bundix.nix b/pkgs/development/interpreters/ruby/bundix.nix
deleted file mode 100644
index 691b4c5e9799..000000000000
--- a/pkgs/development/interpreters/ruby/bundix.nix
+++ /dev/null
@@ -1,45 +0,0 @@
-{rubyLibsWith, callPackage, lib, fetchurl, fetchgit}:
-
-let
-
-  sourceInstantiators = {
-    # Many ruby people use `git ls-files` to compose their gemspecs.
-    git = (attrs: fetchgit { inherit (attrs) url rev sha256 leaveDotGit; });
-    url = (attrs: fetchurl { inherit (attrs) url sha256; });
-  };
-
-in
-
-{
-  # Loads a set containing a ruby environment definition. The set's `gemset`
-  # key is expected to contain a set of gems. Optionally, the `ruby_version`
-  # key can be set to a string. A gem definition looks like this:
-  #
-  #  rack-test = {
-  #    name = "rack-test-0.6.2";
-  #    src = {
-  #      type = "url";
-  #      url = "https://rubygems.org/downloads/rack-test-0.6.2.gem";
-  #      sha256 = "01mk715ab5qnqf6va8k3hjsvsmplrfqpz6g58qw4m3l8mim0p4ky";
-  #    };
-  #    dependencies = [ "rack" ];
-  #  };
-  loadRubyEnv = path: config:
-    let
-      expr = import path;
-      gemset = lib.mapAttrs (name: attrs:
-        attrs // {
-          src = (builtins.getAttr attrs.src.type sourceInstantiators) attrs.src;
-          dontBuild = !(attrs.src.type == "git");
-        }
-      ) expr.gemset;
-      ruby = config.ruby;
-      rubyLibs = rubyLibsWith ruby;
-      gems = rubyLibs.importGems gemset (config.gemOverrides or (gemset: {}));
-    in {
-      inherit ruby gems; # TODO: Set ruby using expr.rubyVersion if not given.
-      gemPath = map (drv: "${drv}") (
-        builtins.filter (value: lib.isDerivation value) (lib.attrValues gems)
-      );
-    };
-}
diff --git a/pkgs/development/interpreters/ruby/fixes.nix b/pkgs/development/interpreters/ruby/fixes.nix
index 7314bc2a0083..eebda22263ac 100644
--- a/pkgs/development/interpreters/ruby/fixes.nix
+++ b/pkgs/development/interpreters/ruby/fixes.nix
@@ -21,21 +21,20 @@
 , which, postgresql, v8_3_16_14, clang }:
 
 let
-  id = x: x;
+  const = x: y: x;
   v8 = v8_3_16_14;
 
-  gems = lib.mapAttrs (name: config:
-    if (lib.isDerivation config) then config
-    else (instantiate name config)
+  gems = lib.mapAttrs (name: attrs:
+    if (lib.isDerivation attrs) then attrs
+    else (instantiate name attrs)
   ) gemset;
 
   instantiate = (name: attrs:
     let
-      # Turn dependency strings into actual derivations.
       gemPath = map (name: gems."${name}") (attrs.dependencies or []);
-      fixedAttrs = (fixes."${name}" or id) attrs;
+      fixedAttrs = attrs // (fixes."${name}" or const {}) attrs;
     in
-      buildRubyGem (fixedAttrs // { inherit gemPath; })
+      buildRubyGem (fixedAttrs // { name = "${name}-${attrs.version}"; inherit gemPath; })
   );
 
   fixes = {
diff --git a/pkgs/development/interpreters/ruby/gem.nix b/pkgs/development/interpreters/ruby/gem.nix
index ce0b8e15fec2..b136cb0de9b2 100644
--- a/pkgs/development/interpreters/ruby/gem.nix
+++ b/pkgs/development/interpreters/ruby/gem.nix
@@ -1,13 +1,12 @@
 { ruby, fetchurl, rake, rubygemsFun, makeWrapper, lib, git }:
 
 { name
-, namePrefix ? "ruby${ruby.majorVersion}" + "-"
+, namePrefix ? "${ruby.name}" + "-"
 , buildInputs ? []
 , doCheck ? false # TODO: fix this
 , dontBuild ? true
 , meta ? {}
 , gemPath ? []
-, testTask ? "test"
 , ...} @ attrs:
 
 let
@@ -60,7 +59,10 @@ in ruby.stdenv.mkDerivation (attrs // {
 
     gemspec=`find . -name '*.gemspec'`
     output=`gem build $gemspec`
-    gempkg=`echo $output|grep -oP 'File: \K(.*)'`
+
+    gem build $gemspec | tee .output
+    gempkg=`cat .output | grep -oP 'File: \K(.*)'`
+    rm .output
 
     echo "Gem package built: $gempkg"
 
@@ -103,7 +105,7 @@ in ruby.stdenv.mkDerivation (attrs // {
     mkdir -p $out/nix-support
 
     cat > $out/nix-support/setup-hook <<EOF
-    if [[ "$GEM_PATH" != *$out* ]]; then
+    if [[ "\$GEM_PATH" != *$out* ]]; then
       addToSearchPath GEM_PATH $out/${ruby.gemPath}
     fi
     EOF
diff --git a/pkgs/development/interpreters/ruby/gems.nix b/pkgs/development/interpreters/ruby/import-gems.nix
similarity index 95%
rename from pkgs/development/interpreters/ruby/gems.nix
rename to pkgs/development/interpreters/ruby/import-gems.nix
index 2dd1739d49f7..0efc7a7e2ee2 100644
--- a/pkgs/development/interpreters/ruby/gems.nix
+++ b/pkgs/development/interpreters/ruby/import-gems.nix
@@ -45,12 +45,12 @@ in
   #       buildInputs = [ postgresql ];
   #     });
   #   });
-  importGems = file: args:
+  importGems = file: gemOverrides:
     let
       # 1. Load set of gem names and versions from a bundix-created expression.
       gemset = if (builtins.isAttrs file) then file else (callPackage file { });
       # 2. Allow gems to be overriden by providing a derivation yourself.
-      config = gemset // (args gemset);
+      config = gemset // (gemOverrides gemset);
       # 3.
       gems = fixGems config;
     in gems;
diff --git a/pkgs/development/interpreters/ruby/load-ruby-env.nix b/pkgs/development/interpreters/ruby/load-ruby-env.nix
new file mode 100644
index 000000000000..e2f61d82d8bf
--- /dev/null
+++ b/pkgs/development/interpreters/ruby/load-ruby-env.nix
@@ -0,0 +1,51 @@
+{rubyLibsWith, callPackage, lib, fetchurl, fetchgit}:
+
+let
+
+  sourceInstantiators = {
+    # Many ruby people use `git ls-files` to compose their gemspecs.
+    git = (attrs: fetchgit { inherit (attrs) url rev sha256 leaveDotGit; });
+    url = (attrs: fetchurl { inherit (attrs) url sha256; });
+  };
+
+in
+
+{
+  # Loads a set containing a ruby environment definition. The set's `gemset`
+  # key is expected to contain a set of gems. A gemset definition looks like this:
+  #
+  #  {
+  #    gemset = {
+  #      rack-test = {
+  #        version = "0.6.2";
+  #        src = {
+  #          type = "url";
+  #          url = "https://rubygems.org/downloads/rack-test-0.6.2.gem";
+  #          sha256 = "01mk715ab5qnqf6va8k3hjsvsmplrfqpz6g58qw4m3l8mim0p4ky";
+  #        };
+  #        dependencies = [ "rack" ];
+  #      };
+  #    };
+  #  }
+  loadRubyEnv = expr: config:
+    let
+      expr' =
+        if builtins.isAttrs expr
+        then expr
+        else import expr;
+      gemset = lib.mapAttrs (name: attrs:
+        attrs // {
+          src = (sourceInstantiators."${attrs.src.type}") attrs.src;
+          dontBuild = !(attrs.src.type == "git");
+        }
+      ) expr'.gemset;
+      ruby = config.ruby;
+      rubyLibs = rubyLibsWith ruby;
+      gems = rubyLibs.importGems gemset (config.gemOverrides or (gemset: {}));
+      gemPath = map (drv: "${drv}") (
+        builtins.filter lib.isDerivation (lib.attrValues gems)
+      );
+    in {
+      inherit ruby gems gemPath;
+    };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index e85d18f01edf..3a80854850ac 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -4045,13 +4045,11 @@ let
   ruby_2_0 = ruby_2_0_0;
   ruby_2_1 = ruby_2_1_3;
 
-  rubyLibsWith = ruby: callPackage ../development/interpreters/ruby/gems.nix {
+  rubyLibsWith = ruby: callPackage ../development/interpreters/ruby/import-gems.nix {
     inherit ruby;
   };
 
-  loadRubyEnv = (callPackage ../development/interpreters/ruby/bundix.nix {
-    inherit rubyLibsWith;
-  }).loadRubyEnv;
+  loadRubyEnv = (callPackage ../development/interpreters/ruby/load-ruby-env.nix { }).loadRubyEnv;
 
   rubyLibs_1_8_7 = rubyLibsWith ruby_1_8_7;
   rubyLibs_1_9_3 = rubyLibsWith ruby_1_9_3;