diff --git a/src/pegasus/request.lua b/src/pegasus/request.lua
index d217908..3a9c828 100644
--- a/src/pegasus/request.lua
+++ b/src/pegasus/request.lua
@@ -91,12 +91,21 @@ function Request:parseFirstLine()
   self.querystring = self:parseUrlEncoded(querystring)
 end
 
-function Request:parseUrlEncoded(value)
+function Request:parseUrlEncoded(data)
   local output = {}
 
-  if value then
-    for k, v in  string.gmatch(value, Request.PATTERN_QUERY_STRING) do
-        output[k] = v
+  if data then
+    for key, value in  string.gmatch(data, Request.PATTERN_QUERY_STRING) do
+      if key and value then
+        local v = output[key]
+        if not v then
+          output[key] = value
+        elseif type(v) == "string" then
+          output[key] = { v, value }
+        else -- v is a table
+          v[#v + 1] = value
+        end
+      end
     end
   end
 
@@ -128,20 +137,29 @@ function Request:headers()
 
   local data = self.client:receive()
 
+  local headers = {}
   while (data ~= nil) and (data:len() > 0) do
     local key, value = string.match(data, Request.PATTERN_HEADER)
 
     if key and value then
-      self._headers[key] = value
+      local v = headers[key]
+      if not v then
+        headers[key] = value
+      elseif type(v) == "string" then
+        headers[key] = { v, value }
+      else -- t == "table", v is a table
+        v[#v + 1] = value
+      end
     end
 
     data = self.client:receive()
   end
 
   self._headerParsed = true
-  self._contentLength = tonumber(self._headers["Content-Length"] or 0)
+  self._contentLength = tonumber(headers["Content-Length"] or 0)
+  self._headers = headers
 
-  return self._headers
+  return headers
 end
 
 function Request:receiveBody(size)
diff --git a/src/pegasus/response.lua b/src/pegasus/response.lua
index 67785f1..1a37f64 100644
--- a/src/pegasus/response.lua
+++ b/src/pegasus/response.lua
@@ -113,13 +113,19 @@ function Response:statusCode(statusCode, statusText)
 end
 
 function Response:_getHeaders()
-  local headers = ''
-
-  for key, value in pairs(self._headers) do
-    headers = headers .. key .. ': ' .. value .. '\r\n'
+  local headers = {}
+
+  for header_name, header_value in pairs(self._headers) do
+    if type(header_value) == "table" and #header_value > 0 then
+      for _, sub_value in ipairs(header_value) do
+        headers[#headers + 1] = header_name .. ': ' .. sub_value .. '\r\n'
+      end
+    else
+      headers[#headers + 1] = header_name .. ': ' .. header_value .. '\r\n'
+    end
   end
 
-  return headers
+  return table.concat(headers)
 end
 
 function Response:writeDefaultErrorMessage(statusCode)
diff --git a/test/unit/request_spec.lua b/test/unit/request_spec.lua
index 5685e99..0fa2d9c 100644
--- a/test/unit/request_spec.lua
+++ b/test/unit/request_spec.lua
@@ -59,17 +59,23 @@ describe('require', function()
 
   test('headers', function()
     local request = getInstance(
-      { 'GET /Makefile?a=b&c=d HTTP/1.1', 'a: A', 'b: B', '', 'C=3', '' }
+      { 'GET /Makefile?a=b&c=d&e=1&e=2 HTTP/1.1', 'a: A', 'b: B', 'c: X', 'c: Y', '', 'C=3', '' }
     )
 
     assert.are.same(
-      request:headers(),
-      { ['a'] = 'A', ['b'] = 'B' }
+      request:headers(), {
+        a = 'A',
+        b = 'B',
+        c = { 'X', 'Y' },
+      }
     )
 
     assert.are.same(
-      request.querystring,
-      { ['a'] = 'b', ['c'] = 'd' }
+      request.querystring, {
+        a = 'b',
+        c = 'd',
+        e = { '1', '2' },
+      }
     )
   end)
 
diff --git a/test/unit/response_spec.lua b/test/unit/response_spec.lua
index 2df4289..cbf598c 100644
--- a/test/unit/response_spec.lua
+++ b/test/unit/response_spec.lua
@@ -96,6 +96,14 @@ describe('response', function()
       assert.equal(headers['Age'], 15163)
       assert.equal(headers['Connection'], 'keep-alive')
     end)
+
+    it("should allow multi-value/duplicate headers", function()
+      local response = Response:new({})
+      response:addHeader('My-Header', { 'value 1', 'value 2' })
+      local expected = "My-Header: value 1" .. "\r\n"
+                    .. "My-Header: value 2" .. "\r\n"
+      assert.equal(expected, response:_getHeaders())
+    end)
   end)
 
   describe('status code', function()