diff --git a/pkgs/development/interpreters/ruby/default.nix b/pkgs/development/interpreters/ruby/default.nix
index bdeb5d02065b..7126a5140c36 100644
--- a/pkgs/development/interpreters/ruby/default.nix
+++ b/pkgs/development/interpreters/ruby/default.nix
@@ -1,32 +1,35 @@
-{ stdenv, lib, fetchurl, fetchFromSavannah, fetchFromGitHub
+{ stdenv, lib, fetchurl, fetchpatch, fetchFromSavannah, fetchFromGitHub
 , zlib, openssl, gdbm, ncurses, readline, groff, libyaml, libffi, autoreconfHook, bison
 , autoconf, darwin ? null
 , buildEnv, bundler, bundix
 } @ args:
 
 let
-  op = stdenv.lib.optional;
-  ops = stdenv.lib.optionals;
-  opString = stdenv.lib.optionalString;
+  op = lib.optional;
+  ops = lib.optionals;
+  opString = lib.optionalString;
   patchSet = import ./rvm-patchsets.nix { inherit fetchFromGitHub; };
   config = import ./config.nix { inherit fetchFromSavannah; };
   rubygemsSrc = import ./rubygems-src.nix { inherit fetchurl; };
+  rubygemsPatch = fetchpatch {
+    url = "https://github.com/zimbatm/rubygems/compare/v2.6.6...v2.6.6-nix.patch";
+    sha256 = "0297rdb1m6v75q8665ry9id1s74p9305dv32l95ssf198liaihhd";
+  };
   unpackdir = obj:
     lib.removeSuffix ".tgz"
       (lib.removeSuffix ".tar.gz" obj.name);
 
-  generic = { majorVersion, minorVersion, teenyVersion, patchLevel, sha256 }: let
-    versionNoPatch = "${majorVersion}.${minorVersion}.${teenyVersion}";
-    version = "${versionNoPatch}-p${patchLevel}";
-    fullVersionName = if patchLevel != "0" && stdenv.lib.versionOlder versionNoPatch "2.1"
-      then version
-      else versionNoPatch;
-    tag = "v" + stdenv.lib.replaceChars ["." "p" "-"] ["_" "_" ""] fullVersionName;
-    isRuby20 = majorVersion == "2" && minorVersion == "0";
-    isRuby21 = majorVersion == "2" && minorVersion == "1";
+  # Contains the ruby version heuristics
+  rubyVersion = import ./ruby-version.nix { inherit lib; };
+
+  generic = { version, sha256 }: let
+    ver = version;
+    tag = ver.gitTag;
+    isRuby20 = ver.majMin == "2.0";
+    isRuby21 = ver.majMin == "2.1";
     baseruby = self.override { useRailsExpress = false; };
     self = lib.makeOverridable (
-      { stdenv, lib, fetchurl, fetchFromSavannah, fetchFromGitHub
+      { stdenv, lib, fetchurl, fetchpatch, fetchFromSavannah, fetchFromGitHub
       , useRailsExpress ? true
       , zlib, zlibSupport ? true
       , openssl, opensslSupport ? true
@@ -46,13 +49,11 @@ let
           rev    = tag;
           sha256 = sha256.git;
         } else fetchurl {
-          url = "http://cache.ruby-lang.org/pub/ruby/${majorVersion}.${minorVersion}/ruby-${fullVersionName}.tar.gz";
+          url = "http://cache.ruby-lang.org/pub/ruby/${ver.majMin}/ruby-${ver}.tar.gz";
           sha256 = sha256.src;
         };
       in
       stdenv.mkDerivation rec {
-        inherit version;
-
         name = "ruby-${version}";
 
         srcs = [ rubySrc rubygemsSrc ];
@@ -85,13 +86,16 @@ let
         hardeningDisable = lib.optional isRuby20 [ "format" ];
 
         patches =
-          [ ./gem_hook.patch ] ++
           (import ./patchsets.nix {
-            inherit patchSet useRailsExpress ops patchLevel;
-          })."${versionNoPatch}";
+            inherit patchSet useRailsExpress ops;
+            patchLevel = ver.patchLevel;
+          })."${ver.majMinTiny}";
 
         postUnpack = ''
           cp -r ${unpackdir rubygemsSrc} ${sourceRoot}/rubygems
+          pushd ${sourceRoot}/rubygems
+          patch -p1 < ${rubygemsPatch}
+          popd
         '' + opString isRuby21 ''
           rm "$sourceRoot/enc/unicode/name2ctype.h"
         '';
@@ -152,25 +156,28 @@ let
         };
 
         passthru = rec {
-          inherit majorVersion minorVersion teenyVersion patchLevel version;
+          version = ver;
           rubyEngine = "ruby";
           baseRuby = baseruby;
-          libPath = "lib/${rubyEngine}/${versionNoPatch}";
-          gemPath = "lib/${rubyEngine}/gems/${versionNoPatch}";
+          libPath = "lib/${rubyEngine}/${ver.libDir}";
+          gemPath = "lib/${rubyEngine}/gems/${ver.libDir}";
           devEnv = import ./dev.nix {
             inherit buildEnv bundler bundix;
             ruby = self;
           };
+
+          # deprecated 2016-09-21
+          majorVersion = ver.major;
+          minorVersion = ver.minor;
+          teenyVersion = ver.tiny;
+          patchLevel = ver.patchLevel;
         };
       }
     ) args; in self;
 
 in {
   ruby_1_9_3 = generic {
-    majorVersion = "1";
-    minorVersion = "9";
-    teenyVersion = "3";
-    patchLevel = "551";
+    version = rubyVersion "1" "9" "3" "p551";
     sha256 = {
       src = "1s2ibg3s2iflzdv7rfxi1qqkvdbn2dq8gxdn0nxrb77ls5ffanxv";
       git = "1r9xzzxmci2ajb34qb4y1w424mz878zdgzxkfp9w60agldxnb36s";
@@ -178,10 +185,7 @@ in {
   };
 
   ruby_2_0_0 = generic {
-    majorVersion = "2";
-    minorVersion = "0";
-    teenyVersion = "0";
-    patchLevel = "647";
+    version = rubyVersion "2" "0" "0" "p647";
     sha256 = {
       src = "1v2vbvydarcx5801gx9lc6gr6dfi0i7qbzwhsavjqbn79rdsz2n8";
       git = "186pf4q9xymzn4zn1sjppl1skrl5f0159ixz5cz8g72dmmynq3g3";
@@ -189,10 +193,7 @@ in {
   };
 
   ruby_2_1_10 = generic {
-    majorVersion = "2";
-    minorVersion = "1";
-    teenyVersion = "10";
-    patchLevel = "0";
+    version = rubyVersion "2" "1" "10" "";
     sha256 = {
       src = "086x66w51lg41abjn79xb7f6xsryymkcc3nvakmkjnjyg96labpv";
       git = "133phd5r5y0np5lc9nqif93l7yb13yd52aspyl6c46z5jhvhyvfi";
@@ -200,10 +201,7 @@ in {
   };
 
   ruby_2_2_5 = generic {
-    majorVersion = "2";
-    minorVersion = "2";
-    teenyVersion = "5";
-    patchLevel = "0";
+    version = rubyVersion "2" "2" "5" "";
     sha256 = {
       src = "1qrmlcyc0cy9hgafb1wny2h90rjyyh6d72nvr2h4xjm4jwbb7i1h";
       git = "0k0av6ypyq08c9axm721f0xi2bcp1443l7ydbxv4v8x4vsxdkmq2";
@@ -211,10 +209,7 @@ in {
   };
 
   ruby_2_3_1 = generic {
-    majorVersion = "2";
-    minorVersion = "3";
-    teenyVersion = "1";
-    patchLevel = "0";
+    version = rubyVersion "2" "3" "1" "";
     sha256 = {
       src = "1kbxg72las93w0y553cxv3lymy2wvij3i3pg1y9g8aq3na676z5q";
       git = "0dv1rf5f9lj3icqs51bq7ljdcf17sdclmxm9hilwxps5l69v5q9r";
diff --git a/pkgs/development/interpreters/ruby/gem_hook.patch b/pkgs/development/interpreters/ruby/gem_hook.patch
deleted file mode 100644
index 78ff9ddbb1a9..000000000000
--- a/pkgs/development/interpreters/ruby/gem_hook.patch
+++ /dev/null
@@ -1,21 +0,0 @@
-diff --git a/rubygems/lib/rubygems/installer.rb b/rubygems/lib/rubygems/installer.rb
-index a88d393..8612901 100644
---- a/rubygems/lib/rubygems/installer.rb
-+++ b/rubygems/lib/rubygems/installer.rb
-@@ -766,7 +766,15 @@ TEXT
-   # Ensures that files can't be installed outside the gem directory.
- 
-   def extract_files
--    @package.extract_files gem_dir
-+    ret = @package.extract_files gem_dir
-+    if ENV['NIX_POST_EXTRACT_FILES_HOOK']
-+      puts
-+      puts "running NIX_POST_EXTRACT_FILES_HOOK #{ENV['NIX_POST_EXTRACT_FILES_HOOK']} #{gem_dir}"
-+      system("#{ENV['NIX_POST_EXTRACT_FILES_HOOK']} #{gem_dir}")
-+      puts "running NIX_POST_EXTRACT_FILES_HOOK done"
-+      puts
-+    end
-+    ret
-   end
- 
-   ##
diff --git a/pkgs/development/interpreters/ruby/ruby-version.nix b/pkgs/development/interpreters/ruby/ruby-version.nix
new file mode 100644
index 000000000000..b1cbbfc216dc
--- /dev/null
+++ b/pkgs/development/interpreters/ruby/ruby-version.nix
@@ -0,0 +1,63 @@
+# Contains the ruby version heuristics
+{ lib }:
+with lib;
+let
+  # The returned set should be immutable
+  rubyVersion = major: minor: tiny: tail:
+    rec {
+      inherit major minor tiny tail;
+
+      # Contains the patch number "223" if tail is "p223" or null
+      patchLevel =
+        let
+          p = removePrefix "p" tail;
+          isPosInt = num:
+            0 == stringLength
+              (replaceStrings
+              ["0" "1" "2" "3" "4" "5" "6" "7" "8" "9"]
+              [""  ""  ""  ""  ""  ""  ""  ""  ""  "" ]
+              num);
+        in
+          if hasPrefix "p" tail && isPosInt p then p
+          else null;
+
+      # Shortcuts
+      majMin = "${major}.${minor}";
+      majMinTiny = "${major}.${minor}.${tiny}";
+
+      # Ruby separates lib and gem folders by ABI version which isn't very
+      # consistent.
+      libDir =
+        if versionAtLeast majMinTiny "2.1.0" then
+          "${majMin}.0"
+        else if versionAtLeast majMinTiny "2.0.0" then
+          "2.0.0"
+        else if versionAtLeast majMinTiny "1.9.1" then
+          "1.9.1"
+        else
+          throw "version ${majMinTiny} is not supported";
+
+      # How ruby releases are tagged on github.com/ruby/ruby
+      gitTag =
+        let
+          base = "v${major}_${minor}_${tiny}";
+        in
+          if patchLevel != null then
+            "${base}_${patchLevel}"
+          else
+            if tail != "" then
+              "${base}_${tail}"
+            else
+              base;
+
+      # Implements the builtins.toString interface.
+      __toString = self:
+        self.majMinTiny + (
+          if self.patchLevel != null then
+            "-p${self.patchLevel}"
+          else if self.tail != "" then
+            "-${self.tail}"
+          else "");
+    };
+in
+  rubyVersion
diff --git a/pkgs/development/ruby-modules/gem/default.nix b/pkgs/development/ruby-modules/gem/default.nix
index 347c4a79c596..ade6659c400b 100644
--- a/pkgs/development/ruby-modules/gem/default.nix
+++ b/pkgs/development/ruby-modules/gem/default.nix
@@ -184,6 +184,7 @@ stdenv.mkDerivation (attrs // {
       --install-dir "$GEM_HOME" \
       --build-root '/' \
       --backtrace \
+      --no-env-shebang \
       ${documentFlag} \
       $gempkg $gemFlags -- $buildFlags