diff --git a/.ruby-version b/.ruby-version
index 3f36e23..99a49eb 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-jruby-1.7.17
+jruby-1.7.23
diff --git a/crimp.gemspec b/crimp.gemspec
index 2704f12..e61bd40 100644
--- a/crimp.gemspec
+++ b/crimp.gemspec
@@ -7,7 +7,7 @@ Gem::Specification.new do |spec|
   spec.name          = "crimp"
   spec.version       = Crimp::VERSION
   spec.authors       = ["BBC News"]
-  spec.email         = ["FutureMediaNewsRubyGems@bbc.co.uk"]
+  spec.email         = ["D&ENewsFrameworksTeam@bbc.co.uk"]
   spec.summary       = %q{Creating an md5 hash of a number, string, array, or hash in Ruby}
   spec.description   = <<-EOS.gsub /^\s+/, ""
                          Shamelessly lifted from http://stackoverflow.com/questions/6461812/creating-an-md5-hash-of-a-number-string-array-or-hash-in-ruby
diff --git a/lib/crimp.rb b/lib/crimp.rb
index ad75a86..e39d8ea 100644
--- a/lib/crimp.rb
+++ b/lib/crimp.rb
@@ -1,6 +1,13 @@
 require 'crimp/version'
 require 'digest'
 
+class Numeric
+  # see http://patshaughnessy.net/2014/1/9/how-big-is-a-bignum
+  def bignum?
+    self >= 4611686018427387904
+  end
+end
+
 module Crimp
   def self.signature(obj)
     Digest::MD5.hexdigest stringify(obj)
@@ -44,6 +51,24 @@ def self.parse_hash(hash)
   end
 
   def self.to_string(obj)
-    "#{obj}#{obj.class}"
+    "#{obj}#{legacy_class(obj)}"
+  end
+
+  # This is for legacy/compatibilty reason:
+  #
+  # Ruby 2.1
+  # 2.class => Fixnum
+  # Ruby >= 2.4
+  # 2.class => Integer
+  #
+  # Say you have a huge number of stored keys and you migrate your app from 2.1 to >= 2.4
+  # this would cause a change of the signature for a subset of the keys which would be hard
+  # to debug especially for nested data structures.
+  #
+  def self.legacy_class(obj)
+    return obj.class unless obj.is_a?(Numeric)
+    return 'Float'   if obj.is_a?(Float)
+    return 'Bignum'  if obj.bignum?
+    'Fixnum'
   end
 end
diff --git a/lib/crimp/version.rb b/lib/crimp/version.rb
index 0e6759f..3092bd4 100644
--- a/lib/crimp/version.rb
+++ b/lib/crimp/version.rb
@@ -1,3 +1,3 @@
 module Crimp
-  VERSION = '0.1.2'.freeze
+  VERSION = '0.2.0'.freeze
 end
diff --git a/spec/crimp_spec.rb b/spec/crimp_spec.rb
index bb96378..623aa97 100644
--- a/spec/crimp_spec.rb
+++ b/spec/crimp_spec.rb
@@ -1,17 +1,16 @@
 require 'spec_helper'
 
 describe Crimp do
-  let (:hash) { { a: { b: 'b', c: 'c' }, d: 'd' } }
-  let (:hash_unordered) { { d: 'd', a: { c: 'c', b: 'b' } } }
-  let (:array) { [1, 2, 3, [4, [5, 6]]] }
-  let (:array_unordered) { [3, 2, 1, [[5, 6], 4]] }
+  let(:hash) { { a: { b: 'b', c: 'c' }, d: 'd' } }
+  let(:hash_with_numbers) { { a: { b: 1, c: 3.14 }, d: 'd' } }
+  let(:hash_unordered) { { d: 'd', a: { c: 'c', b: 'b' } } }
+  let(:array) { [1, 2, 3, [4, [5, 6]]] }
+  let(:array_unordered) { [3, 2, 1, [[5, 6], 4]] }
 
   describe '.signature' do
     context 'given a Hash' do
-      specify { expect(subject.signature(hash)).to be_a String }
-
       it 'returns MD5 hash of stringified Hash' do
-        expect(subject.signature(hash)).to eq(Digest::MD5.hexdigest(subject.stringify(hash)))
+        expect(subject.signature(hash)).to eq('68d07febc4f47f56fa6ef5de063a77b1')
       end
 
       it 'does not modify original hash' do
@@ -24,11 +23,15 @@
       end
     end
 
-    context 'given an Array' do
-      specify { expect(subject.signature(array)).to be_a String }
+    context 'Given an hash with numbers' do
+      it 'returns MD5 hash of stringified hash' do
+        expect(subject.signature(hash_with_numbers)).to eq 'b1fec09904b6ff36c92e3bd48234def7'
+      end
+    end
 
+    context 'given an Array' do
       it 'returns MD5 hash of stringified Array' do
-        expect(subject.signature(array)).to eq(Digest::MD5.hexdigest(subject.stringify(array)))
+        expect(subject.signature(array)).to eq('4dc4e1161c9315db0bc43c0201b3ec05')
       end
 
       it 'does not modify original array' do
@@ -40,12 +43,28 @@
         expect(original_array).to eq(expected_array)
       end
     end
+
+    context 'Given an integer' do
+      it 'returns MD5 hash of an Integer' do
+        expect(subject.signature(123)).to eq '519d3381631851be66711f6d7dfbb4f8'
+      end
+    end
+
+    context 'Given an Bignum' do
+      it 'returns MD5 hash of a Bignum' do
+        expect(subject.signature(9999999999999999999)).to eq 'f00e75abca720e18fd4213e2a6de96c6'
+      end
+    end
+
+    context 'Given an float' do
+      it 'returns MD5 hash of a Float' do
+        expect(subject.signature(3.14)).to eq 'b07d506e3701fddd083ae9095df43218'
+      end
+    end
   end
 
   describe '.stringify' do
     context 'given a Hash' do
-      specify { expect(subject.stringify(hash)).to be_a String }
-
       it 'returns equal strings for differently ordered hashes' do
         expect(subject.stringify(hash)).to eq(subject.stringify(hash_unordered))
       end