diff --git a/README.md b/README.md
index 15b20d8..a783c2a 100644
--- a/README.md
+++ b/README.md
@@ -89,7 +89,7 @@ Nori lets you specify a custom formula to convert XML tags to Hash keys using `c
 Nori.new.parse('<userResponse><accountStatus>active</accountStatus></userResponse>')
 # => {"userResponse"=>{"accountStatus"=>"active"}}
 
-parser = Nori.new(:convert_tags_to => lambda { |tag| tag.snakecase.to_sym })
+parser = Nori.new(:convert_tags_to => lambda { |tag| Nori::StringUtils.snakecase(tag).to_sym })
 parser.parse('<userResponse><accountStatus>active</accountStatus></userResponse>')
 # => {:user_response=>{:account_status=>"active"}}
 ```
diff --git a/lib/nori/core_ext.rb b/lib/nori/core_ext.rb
index 09cc095..0a5ad5b 100644
--- a/lib/nori/core_ext.rb
+++ b/lib/nori/core_ext.rb
@@ -1,2 +1,2 @@
-require "nori/core_ext/string"
+require "nori/string_utils"
 require "nori/core_ext/hash"
diff --git a/lib/nori/core_ext/hash.rb b/lib/nori/core_ext/hash.rb
index 44153d7..b032451 100644
--- a/lib/nori/core_ext/hash.rb
+++ b/lib/nori/core_ext/hash.rb
@@ -27,7 +27,7 @@ def normalize_param(key, value)
       #     #=> 'one="1" two="TWO"'
       def to_xml_attributes
         map do |k, v|
-          %{#{k.to_s.snakecase.sub(/^(.{1,1})/) { |m| m.downcase }}="#{v}"}
+          %{#{StringUtils.snakecase(k.to_s).sub(/^(.{1,1})/) { |m| m.downcase }}="#{v}"}
         end.join(' ')
       end
 
diff --git a/lib/nori/core_ext/string.rb b/lib/nori/core_ext/string.rb
deleted file mode 100644
index 27b4308..0000000
--- a/lib/nori/core_ext/string.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-class Nori
-  module CoreExt
-    module String
-
-      # Returns the String in snake_case.
-      def snakecase
-        str = dup
-        str.gsub!(/::/, '/')
-        str.gsub!(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
-        str.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
-        str.tr! ".", "_"
-        str.tr! "-", "_"
-        str.downcase!
-        str
-      end unless method_defined?(:snakecase)
-
-    end
-  end
-end
-
-String.send :include, Nori::CoreExt::String
diff --git a/lib/nori/string_utils.rb b/lib/nori/string_utils.rb
new file mode 100644
index 0000000..da6d990
--- /dev/null
+++ b/lib/nori/string_utils.rb
@@ -0,0 +1,18 @@
+class Nori
+  module StringUtils
+    # Converts a string to snake case.
+    #
+    # @param inputstring [String] The string to be converted to snake case.
+    # @return [String] A copy of the input string converted to snake case.
+    def self.snakecase(inputstring)
+      str = inputstring.dup
+      str.gsub!(/::/, '/')
+      str.gsub!(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
+      str.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
+      str.tr!(".", "_")
+      str.tr!("-", "_")
+      str.downcase!
+      str
+    end
+  end
+end
diff --git a/spec/nori/api_spec.rb b/spec/nori/api_spec.rb
index b4e8691..bd67627 100644
--- a/spec/nori/api_spec.rb
+++ b/spec/nori/api_spec.rb
@@ -55,7 +55,7 @@
     it "converts all tags by a given formula" do
       xml = '<userResponse id="1"><accountStatus>active</accountStatus></userResponse>'
 
-      snakecase_symbols = lambda { |tag| tag.snakecase.to_sym }
+      snakecase_symbols = lambda { |tag| Nori::StringUtils.snakecase(tag).to_sym }
       nori = nori(:convert_tags_to => snakecase_symbols)
 
       expect(nori.parse(xml)).to eq({ :user_response => { :@id => "1", :account_status => "active" } })
diff --git a/spec/nori/core_ext/string_spec.rb b/spec/nori/core_ext/string_spec.rb
deleted file mode 100644
index 93989b7..0000000
--- a/spec/nori/core_ext/string_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require "spec_helper"
-
-describe String do
-
-  describe "#snakecase" do
-    it "lowercases one word CamelCase" do
-      expect("Merb".snakecase).to eq("merb")
-    end
-
-    it "makes one underscore snakecase two word CamelCase" do
-      expect("MerbCore".snakecase).to eq("merb_core")
-    end
-
-    it "handles CamelCase with more than 2 words" do
-      expect("SoYouWantContributeToMerbCore".snakecase).to eq("so_you_want_contribute_to_merb_core")
-    end
-
-    it "handles CamelCase with more than 2 capital letter in a row" do
-      expect("CNN".snakecase).to eq("cnn")
-      expect("CNNNews".snakecase).to eq("cnn_news")
-      expect("HeadlineCNNNews".snakecase).to eq("headline_cnn_news")
-    end
-
-    it "does NOT change one word lowercase" do
-      expect("merb".snakecase).to eq("merb")
-    end
-
-    it "leaves snake_case as is" do
-      expect("merb_core".snakecase).to eq("merb_core")
-    end
-  end
-
-end
diff --git a/spec/nori/string_utils_spec.rb b/spec/nori/string_utils_spec.rb
new file mode 100644
index 0000000..b577592
--- /dev/null
+++ b/spec/nori/string_utils_spec.rb
@@ -0,0 +1,33 @@
+require "spec_helper"
+
+describe Nori::StringUtils do
+
+  describe ".snakecase" do
+    it "lowercases one word CamelCase" do
+      expect(Nori::StringUtils.snakecase("Merb")).to eq("merb")
+    end
+
+    it "makes one underscore snakecase two word CamelCase" do
+      expect(Nori::StringUtils.snakecase("MerbCore")).to eq("merb_core")
+    end
+
+    it "handles CamelCase with more than 2 words" do
+      expect(Nori::StringUtils.snakecase("SoYouWantContributeToMerbCore")).to eq("so_you_want_contribute_to_merb_core")
+    end
+
+    it "handles CamelCase with more than 2 capital letter in a row" do
+      expect(Nori::StringUtils.snakecase("CNN")).to eq("cnn")
+      expect(Nori::StringUtils.snakecase("CNNNews")).to eq("cnn_news")
+      expect(Nori::StringUtils.snakecase("HeadlineCNNNews")).to eq("headline_cnn_news")
+    end
+
+    it "does NOT change one word lowercase" do
+      expect(Nori::StringUtils.snakecase("merb")).to eq("merb")
+    end
+
+    it "leaves snake_case as is" do
+      expect(Nori::StringUtils.snakecase("merb_core")).to eq("merb_core")
+    end
+  end
+
+end