diff --git a/lib/fakefs/dir.rb b/lib/fakefs/dir.rb
index 32c5234..b2d84fd 100644
--- a/lib/fakefs/dir.rb
+++ b/lib/fakefs/dir.rb
@@ -107,6 +107,52 @@ module FakeFS
       FileSystem.current_dir.to_s
     end
 
+    # This code has been borrowed from Rubinius
+    def self.mktmpdir(prefix_suffix = nil, tmpdir = nil)
+      case prefix_suffix
+      when nil
+        prefix = "d"
+        suffix = ""
+      when String
+        prefix = prefix_suffix
+        suffix = ""
+      when Array
+        prefix = prefix_suffix[0]
+        suffix = prefix_suffix[1]
+      else
+        raise ArgumentError, "unexpected prefix_suffix: #{prefix_suffix.inspect}"
+      end
+
+      t = Time.now.strftime("%Y%m%d")
+      n = nil
+
+      begin
+        path = "#{tmpdir}/#{prefix}#{t}-#{$$}-#{rand(0x100000000).to_s(36)}"
+        path << "-#{n}" if n
+        path << suffix
+        mkdir(path, 0700)
+      rescue Errno::EEXIST
+        n ||= 0
+        n += 1
+        retry
+      end
+
+      if block_given?
+        begin
+          yield path
+        ensure
+          require 'fileutils'
+          # This here was using FileUtils.remove_entry_secure instead of just
+          # .rm_r. However, the security concerns that apply to
+          # .rm_r/.remove_entry_secure shouldn't apply to a test fake
+          # filesystem. :^)
+          FileUtils.rm_r path
+        end
+      else
+        path
+      end
+    end
+
     class << self
       alias_method :getwd, :pwd
       alias_method :rmdir, :delete
diff --git a/lib/fakefs/safe.rb b/lib/fakefs/safe.rb
index 4f2f822..a1b804c 100644
--- a/lib/fakefs/safe.rb
+++ b/lib/fakefs/safe.rb
@@ -9,4 +9,3 @@ require 'fakefs/fileutils'
 require 'fakefs/file'
 require 'fakefs/file_test'
 require 'fakefs/dir'
-require 'fakefs/tmpdir'
diff --git a/lib/fakefs/tmpdir.rb b/lib/fakefs/tmpdir.rb
deleted file mode 100644
index db8d79f..0000000
--- a/lib/fakefs/tmpdir.rb
+++ /dev/null
@@ -1,50 +0,0 @@
-require 'fakefs/fileutils'
-
-module FakeFS
-  class Dir
-    def Dir::mktmpdir(prefix_suffix=nil, tmpdir=nil)
-      # This code has been borrowed from Rubinius. Thanks, guys! :-)
-      
-      case prefix_suffix
-      when nil
-        prefix = "d"
-        suffix = ""
-      when String
-        prefix = prefix_suffix
-        suffix = ""
-      when Array
-        prefix = prefix_suffix[0]
-        suffix = prefix_suffix[1]
-      else
-        raise ArgumentError, "unexpected prefix_suffix: #{prefix_suffix.inspect}"
-      end
-      tmpdir ||= Dir.tmpdir
-      t = Time.now.strftime("%Y%m%d")
-      n = nil
-      begin
-        path = "#{tmpdir}/#{prefix}#{t}-#{$$}-#{rand(0x100000000).to_s(36)}"
-        path << "-#{n}" if n
-        path << suffix
-        Dir.mkdir(path, 0700)
-      rescue Errno::EEXIST
-        n ||= 0
-        n += 1
-        retry
-      end
-
-      if block_given?
-        begin
-          yield path
-        ensure
-          # This here was using FileUtils.remove_entry_secure instead of just
-          # .rm_r. However, the security concerns that apply to
-          # .rm_r/.remove_entry_secure shouldn't apply to a test fake
-          # filesystem. :^)
-          FileUtils.rm_r path
-        end
-      else
-        path
-      end
-    end
-  end
-end