diff --git a/lib/pact/consumer/mock_service/rack_request_helper.rb b/lib/pact/consumer/mock_service/rack_request_helper.rb
index 8d85108..0d97211 100644
--- a/lib/pact/consumer/mock_service/rack_request_helper.rb
+++ b/lib/pact/consumer/mock_service/rack_request_helper.rb
@@ -38,14 +38,25 @@ def request_as_hash_from env
 
       def headers_from env
         headers = env.reject{ |key, value| !(key.start_with?("HTTP") || key == 'CONTENT_TYPE' || key == 'CONTENT_LENGTH')}
-        headers.inject({}) do | hash, header |
+        dasherized_headers = headers.inject({}) do | hash, header |
           hash[standardise_header(header.first)] = header.last
           hash
         end
+        # This header is set in lib/pact/mock_service/server/webrick_request_monkeypatch.rb to allow use to
+        # restore the original header names with underscores.
+        restore_underscored_header_names(dasherized_headers, (env['X_PACT_UNDERSCORED_HEADER_NAMES'] || '').split(","))
       end
 
       def standardise_header header
-        header.gsub(/^HTTP_/, '').split("_").collect{|word| word[0] + word[1..-1].downcase}.join("-")
+        header.gsub(/^HTTP_/, '').split(/[_-]/).collect{|word| word[0].upcase + word[1..-1].downcase}.join("-")
+      end
+
+      def restore_underscored_header_names dasherized_headers, original_header_names
+        original_header_names.each_with_object(dasherized_headers) do | original_header_name, headers |
+          if headers.key?(standardise_header(original_header_name))
+            headers[original_header_name] = headers.delete(standardise_header(original_header_name))
+          end
+        end
       end
     end
   end
diff --git a/lib/pact/mock_service/control_server/run.rb b/lib/pact/mock_service/control_server/run.rb
index 2353fc2..7c3e15b 100644
--- a/lib/pact/mock_service/control_server/run.rb
+++ b/lib/pact/mock_service/control_server/run.rb
@@ -1,4 +1,5 @@
 require 'pact/mock_service/control_server/app'
+require 'pact/mock_service/server/webrick_request_monkeypatch'
 
 module Pact
   module MockService
diff --git a/lib/pact/mock_service/run.rb b/lib/pact/mock_service/run.rb
index f93d717..a9d9d8c 100644
--- a/lib/pact/mock_service/run.rb
+++ b/lib/pact/mock_service/run.rb
@@ -2,6 +2,7 @@
 require 'pact/mock_service/app'
 require 'pact/consumer/mock_service/set_location'
 require 'pact/mock_service/run'
+require 'pact/mock_service/server/webrick_request_monkeypatch'
 
 module Pact
   module MockService
diff --git a/lib/pact/mock_service/server/webrick_request_monkeypatch.rb b/lib/pact/mock_service/server/webrick_request_monkeypatch.rb
new file mode 100644
index 0000000..784407c
--- /dev/null
+++ b/lib/pact/mock_service/server/webrick_request_monkeypatch.rb
@@ -0,0 +1,15 @@
+module WEBrick
+  class HTTPRequest
+    alias_method :pact_original_meta_vars, :meta_vars
+
+    def meta_vars
+      original_underscored_headers = []
+      self.each{|key, val| original_underscored_headers << key if key.include?("_") }
+      # This header allows us to restore the original format (eg. underscored) of the headers
+      # when parsing the incoming Rack env back to a response object.
+      vars = pact_original_meta_vars
+      vars["X_PACT_UNDERSCORED_HEADER_NAMES"] = original_underscored_headers.join(",")
+      vars
+    end
+  end
+end
diff --git a/spec/integration/cli_spec.rb b/spec/integration/cli_spec.rb
index 2be758e..9d470c3 100644
--- a/spec/integration/cli_spec.rb
+++ b/spec/integration/cli_spec.rb
@@ -23,6 +23,13 @@
     expect(response.status).to eq 200
   end
 
+  it "respects headers with underscores" do
+    setup_interaction_with_underscored_header 1234
+    response = invoke_request_with_underscored_header 1234
+    puts response.body unless response.status == 200
+    expect(response.status).to eq 200
+  end
+
   it "sets the X-Pact-Mock-Service-Location header" do
     response = setup_interaction 1234
     expect(response.headers['X-Pact-Mock-Service-Location']).to eq 'http://0.0.0.0:1234'
diff --git a/spec/lib/pact/consumer/mock_service/rack_request_helper_spec.rb b/spec/lib/pact/consumer/mock_service/rack_request_helper_spec.rb
index 1aaa1f7..ffa1cd3 100644
--- a/spec/lib/pact/consumer/mock_service/rack_request_helper_spec.rb
+++ b/spec/lib/pact/consumer/mock_service/rack_request_helper_spec.rb
@@ -63,10 +63,10 @@ class TestSubject
       }
     }
 
+    let(:expected_body) { body }
     context "with a text body" do
       let(:content_type) { "application/x-www-form-urlencoded" }
       let(:body) { 'this is the body' }
-      let(:expected_body) { body }
 
       it "extracts the body" do
         expect(subject.request_as_hash_from(rack_env)).to eq expected_request
@@ -83,6 +83,19 @@ class TestSubject
       end
     end
 
+    context "with X_PACT_UNDERSCORED_HEADER_NAMES" do
+      before do
+        rack_env["HTTP_ACCESS_TOKEN"] = "123"
+        rack_env["X_PACT_UNDERSCORED_HEADER_NAMES"] = "access_token"
+      end
+
+      let(:request) { subject.request_as_hash_from(rack_env) }
 
+      it "sets any headers with underscores back to their original format" do
+        expect(request[:headers]["access_token"]).to eq "123"
+        expect(request[:headers]["X-Something"]).to eq "1, 2"
+        expect(request[:headers].key?("Access-Token")).to be false
+      end
+    end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/support/integration_spec_support.rb b/spec/support/integration_spec_support.rb
index 508196e..23a0c89 100644
--- a/spec/support/integration_spec_support.rb
+++ b/spec/support/integration_spec_support.rb
@@ -82,6 +82,20 @@ def another_expected_interaction
       }.to_json
     end
 
+    def interaction_with_underscored_header
+      {
+        description: "another request for a greeting",
+        request: {
+          method: :get,
+          headers: {'access_token' => '123'},
+          path: '/'
+        },
+        response: {
+          status: 200
+        }
+      }.to_json
+    end
+
     def mock_service_headers
       {
         'Content-Type' => 'application/json',
@@ -108,6 +122,12 @@ def setup_another_interaction port
         mock_service_headers
     end
 
+    def setup_interaction_with_underscored_header port
+      Faraday.post "http://localhost:#{port}/interactions",
+        interaction_with_underscored_header,
+        mock_service_headers
+    end
+
     def invoke_expected_request port
       Faraday.get "http://localhost:#{port}/greeting",
         nil,
@@ -120,6 +140,12 @@ def invoke_another_expected_request port
         {'Foo' => 'Bar'}
     end
 
+    def invoke_request_with_underscored_header port
+      Faraday.get "http://localhost:#{port}/",
+        nil,
+        {'access_token' => '123'}
+    end
+
     def verify port
       Faraday.get "http://localhost:#{port}/interactions/verification",
         nil,