diff --git a/CHANGELOG.md b/CHANGELOG.md
index 872df8c..1139408 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+### 2.2.0 (edge)
+
+* Feature: [#108](https://github.com/savonrb/httpi/pull/108) Make `rubyntlm` gem, an optional dependency.
+
 ### 2.1.0 (2013-07-22)
 
 * Feature: [#75](https://github.com/savonrb/httpi/pull/75) Rack adapter.
diff --git a/httpi.gemspec b/httpi.gemspec
index 2f1bc6e..b2a2e5e 100644
--- a/httpi.gemspec
+++ b/httpi.gemspec
@@ -16,12 +16,12 @@ Gem::Specification.new do |s|
   s.license = 'MIT'
 
   s.add_dependency 'rack'
-  s.add_dependency 'rubyntlm',          '~> 0.3.2'
 
-  s.add_development_dependency 'rake',  '~> 10.0'
-  s.add_development_dependency 'rspec', '~> 2.12'
-  s.add_development_dependency 'mocha', '~> 0.13'
-  s.add_development_dependency 'puma',  '~> 2.3.2'
+  s.add_development_dependency 'rubyntlm', '~> 0.3.2'
+  s.add_development_dependency 'rake',     '~> 10.0'
+  s.add_development_dependency 'rspec',    '~> 2.12'
+  s.add_development_dependency 'mocha',    '~> 0.13'
+  s.add_development_dependency 'puma',     '~> 2.3.2'
 
   s.files = `git ls-files`.split("\n")
   s.require_path = 'lib'
diff --git a/lib/httpi/adapter/net_http.rb b/lib/httpi/adapter/net_http.rb
index 9ad8ea0..59d8f96 100644
--- a/lib/httpi/adapter/net_http.rb
+++ b/lib/httpi/adapter/net_http.rb
@@ -2,10 +2,18 @@
 
 require "httpi/adapter/base"
 require "httpi/response"
-require 'net/ntlm'
 require 'kconv'
 require 'socket'
 
+begin
+  require 'net/ntlm'
+  unless Net::NTLM::VERSION::STRING >= '0.3.2'
+    raise ArgumentError('Invalid version of rubyntlm. Please use v0.3.2+.')
+  end
+rescue LoadError => e
+  HTTPI.logger.debug('Net::NTLM is not available. Install via gem install rubyntlm.')
+end
+
 module HTTPI
   module Adapter
 
@@ -76,6 +84,10 @@ def setup
       end
 
       def negotiate_ntlm_auth(http, &requester)
+        unless Net.const_defined?(:NTLM)
+          HTTPI.logger.fatal('Cannot negotiate ntlm auth if net/ntlm is not present. Perhaps the net/ntlm gem is not installed?')
+        end
+
         # first figure out if we should use NTLM or Negotiate
         nego_auth_response = respond_with(requester.call(http, request_client(:head)))
         if nego_auth_response.headers['www-authenticate'].include? 'Negotiate'
@@ -102,7 +114,7 @@ def negotiate_ntlm_auth(http, &requester)
         if auth_response.headers["WWW-Authenticate"] =~ /(NTLM|Negotiate) (.+)/
           auth_token = $2
           ntlm_message = Net::NTLM::Message.decode64(auth_token)
-          
+
           message_builder = {}
           # copy the username and password from the authorization parameters
           message_builder[:user] = @request.auth.ntlm[0]
@@ -114,7 +126,7 @@ def negotiate_ntlm_auth(http, &requester)
           else
             message_builder[:domain] = ''
           end
-          
+
           ntlm_response = ntlm_message.response(message_builder ,
                                                  {:ntlmv2 => true})
           # Finally add header of Authorization
diff --git a/lib/httpi/version.rb b/lib/httpi/version.rb
index 7343db1..3faa245 100644
--- a/lib/httpi/version.rb
+++ b/lib/httpi/version.rb
@@ -1,5 +1,5 @@
 module HTTPI
 
-  VERSION = "2.1.0"
+  VERSION = "2.2.0"
 
 end
diff --git a/spec/httpi/adapter/net_http_spec.rb b/spec/httpi/adapter/net_http_spec.rb
index f2bc65d..caa50b3 100644
--- a/spec/httpi/adapter/net_http_spec.rb
+++ b/spec/httpi/adapter/net_http_spec.rb
@@ -75,6 +75,17 @@
       response = HTTPI.get(request, adapter)
       response.body.should eq("ntlm-auth")
     end
+
+    it 'fatal logs when net/ntlm is not available, but ntlm authentication was requested' do
+      Net.expects(:const_defined?).with(:NTLM).returns false
+
+      request = HTTPI::Request.new(@server.url + 'ntlm-auth')
+      request.auth.ntlm("testing", "failures")
+      HTTPI.logger.expects(:fatal)
+
+      response = HTTPI.get(request, adapter)
+      response.body.should eq("ntlm-auth")
+    end
   end
 
   # it does not support digest auth