diff --git a/lib/gattica.rb b/lib/gattica.rb
index dc10cb1..068a559 100644
--- a/lib/gattica.rb
+++ b/lib/gattica.rb
@@ -12,7 +12,7 @@
 
 # internal
 require 'gattica/version'
-require 'gattica/core_extensions'
+require 'gattica/hash_extensions'
 require 'gattica/convertible'
 require 'gattica/exceptions'
 require 'gattica/user'
diff --git a/lib/gattica/auth.rb b/lib/gattica/auth.rb
index 9230186..4ea5190 100644
--- a/lib/gattica/auth.rb
+++ b/lib/gattica/auth.rb
@@ -18,6 +18,7 @@ class Auth
     # Try to authenticate the user
     def initialize(http, user)
       options = OPTIONS.merge(user.to_h)
+      options.extend HashExtensions
       
       response, data = http.post(SCRIPT_NAME, options.to_query, HEADERS)
       if response.code != '200'
diff --git a/lib/gattica/convertible.rb b/lib/gattica/convertible.rb
index 9f37e6e..3a269d0 100644
--- a/lib/gattica/convertible.rb
+++ b/lib/gattica/convertible.rb
@@ -10,7 +10,7 @@ def to_h
       instance_variables.each do |var|
         output.merge!({ var[1..-1] => instance_variable_get(var) }) unless var == '@xml'    # exclude the whole XML dump
       end
-      output
+      output.tap { |h| h.include HashExtensions }
     end
     
     # output nice inspect syntax
diff --git a/lib/gattica/core_extensions.rb b/lib/gattica/core_extensions.rb
deleted file mode 100644
index 50ca194..0000000
--- a/lib/gattica/core_extensions.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-class Hash
-  
-  def to_query
-    require 'cgi' unless defined?(CGI) && defined?(CGI::escape)
-    self.collect do |key, value|
-      "#{CGI.escape(key.to_s)}=#{CGI.escape(value.to_s)}"
-    end.sort * '&'
-  end
-  
-  def key
-    self.keys.first if self.length == 1
-  end
-
-  def value
-    self.values.first if self.length == 1
-  end
-  
-  def stringify_keys
-    inject({}) do |options, (key, value)|
-      options[key.to_s] = value
-      options
-    end
-  end
-
-end
diff --git a/lib/gattica/hash_extensions.rb b/lib/gattica/hash_extensions.rb
new file mode 100644
index 0000000..46860dd
--- /dev/null
+++ b/lib/gattica/hash_extensions.rb
@@ -0,0 +1,20 @@
+module Gattica
+  module HashExtensions
+
+    def to_query
+      require 'cgi' unless defined?(CGI) && defined?(CGI::escape)
+      self.collect do |key, value|
+        "#{CGI.escape(key.to_s)}=#{CGI.escape(value.to_s)}"
+      end.sort * '&'
+    end
+
+    def key
+      self.keys.first if self.length == 1
+    end
+
+    def value
+      self.values.first if self.length == 1
+    end
+
+  end
+end
\ No newline at end of file