diff --git a/lib/core/util.js b/lib/core/util.js
index 6f38ffc8a4d..3b9b56cb64d 100644
--- a/lib/core/util.js
+++ b/lib/core/util.js
@@ -213,25 +213,42 @@ function parseHeaders (headers, obj = {}) {
   for (let i = 0; i < headers.length; i += 2) {
     const key = headers[i].toString().toLowerCase()
     let val = obj[key]
+
+    const encoding = key.length === 19 && key === 'content-disposition'
+      ? 'latin1'
+      : 'utf8'
+
     if (!val) {
       if (Array.isArray(headers[i + 1])) {
         obj[key] = headers[i + 1]
       } else {
-        obj[key] = headers[i + 1].toString()
+        obj[key] = headers[i + 1].toString(encoding)
       }
     } else {
       if (!Array.isArray(val)) {
         val = [val]
         obj[key] = val
       }
-      val.push(headers[i + 1].toString())
+      val.push(headers[i + 1].toString(encoding))
     }
   }
   return obj
 }
 
 function parseRawHeaders (headers) {
-  return headers.map(header => header.toString())
+  const ret = []
+  for (let n = 0; n < headers.length; n += 2) {
+    const key = headers[n + 0].toString()
+
+    const encoding = key.length === 19 && key.toLowerCase() === 'content-disposition'
+      ? 'latin1'
+      : 'utf8'
+
+    const val = headers[n + 1].toString(encoding)
+
+    ret.push(key, val)
+  }
+  return ret
 }
 
 function isBuffer (buffer) {
diff --git a/lib/mock/mock-utils.js b/lib/mock/mock-utils.js
index 9dc414d0a35..42ea185cc0e 100644
--- a/lib/mock/mock-utils.js
+++ b/lib/mock/mock-utils.js
@@ -188,7 +188,11 @@ function buildKey (opts) {
 }
 
 function generateKeyValues (data) {
-  return Object.entries(data).reduce((keyValuePairs, [key, value]) => [...keyValuePairs, key, value], [])
+  return Object.entries(data).reduce((keyValuePairs, [key, value]) => [
+    ...keyValuePairs,
+    Buffer.from(`${key}`),
+    Array.isArray(value) ? value.map(x => Buffer.from(`${x}`)) : Buffer.from(`${value}`)
+  ], [])
 }
 
 /**
diff --git a/test/issue-1903.js b/test/issue-1903.js
new file mode 100644
index 00000000000..8478b2d53dd
--- /dev/null
+++ b/test/issue-1903.js
@@ -0,0 +1,77 @@
+'use strict'
+
+const { createServer } = require('http')
+const { test } = require('tap')
+const { request } = require('..')
+
+function createPromise () {
+  const result = {}
+  result.promise = new Promise((resolve) => {
+    result.resolve = resolve
+  })
+  return result
+}
+
+test('should parse content-disposition consistencely', async (t) => {
+  t.plan(5)
+
+  // create promise to allow server spinup in parallel
+  const spinup1 = createPromise()
+  const spinup2 = createPromise()
+  const spinup3 = createPromise()
+
+  // variables to store content-disposition header
+  const header = []
+
+  const server = createServer((req, res) => {
+    res.writeHead(200, {
+      'content-length': 2,
+      'content-disposition': "attachment; filename='år.pdf'"
+    })
+    header.push("attachment; filename='år.pdf'")
+    res.end('OK', spinup1.resolve)
+  })
+  t.teardown(server.close.bind(server))
+  server.listen(0, spinup1.resolve)
+
+  const proxy1 = createServer(async (req, res) => {
+    const { statusCode, headers, body } = await request(`http://localhost:${server.address().port}`, {
+      method: 'GET'
+    })
+    header.push(headers['content-disposition'])
+    delete headers['transfer-encoding']
+    res.writeHead(statusCode, headers)
+    body.pipe(res)
+  })
+  t.teardown(proxy1.close.bind(proxy1))
+  proxy1.listen(0, spinup2.resolve)
+
+  const proxy2 = createServer(async (req, res) => {
+    const { statusCode, headers, body } = await request(`http://localhost:${proxy1.address().port}`, {
+      method: 'GET'
+    })
+    header.push(headers['content-disposition'])
+    delete headers['transfer-encoding']
+    res.writeHead(statusCode, headers)
+    body.pipe(res)
+  })
+  t.teardown(proxy2.close.bind(proxy2))
+  proxy2.listen(0, spinup3.resolve)
+
+  // wait until all server spinup
+  await Promise.all([spinup1.promise, spinup2.promise, spinup3.promise])
+
+  const { statusCode, headers, body } = await request(`http://localhost:${proxy2.address().port}`, {
+    method: 'GET'
+  })
+  header.push(headers['content-disposition'])
+  t.equal(statusCode, 200)
+  t.equal(await body.text(), 'OK')
+
+  // we check header
+  // must not be the same in first proxy
+  t.notSame(header[0], header[1])
+  // chaining always the same value
+  t.equal(header[1], header[2])
+  t.equal(header[2], header[3])
+})