diff --git a/lib/core/util.js b/lib/core/util.js
index f2ead039363..6b9cb1df27a 100644
--- a/lib/core/util.js
+++ b/lib/core/util.js
@@ -228,7 +228,7 @@ function parseHeaders (headers, obj = {}) {
 
     if (!val) {
       if (Array.isArray(headers[i + 1])) {
-        obj[key] = headers[i + 1]
+        obj[key] = headers[i + 1].map(x => x.toString('utf8'))
       } else {
         obj[key] = headers[i + 1].toString('utf8')
       }
diff --git a/test/mock-agent.js b/test/mock-agent.js
index 4145432c2c6..d96a511a167 100644
--- a/test/mock-agent.js
+++ b/test/mock-agent.js
@@ -2594,5 +2594,9 @@ test('MockAgent - headers should be array of strings', async (t) => {
     method: 'GET'
   })
 
-  t.equal(headers['set-cookie'].length, 3)
+  t.same(headers['set-cookie'], [
+    'foo=bar',
+    'bar=baz',
+    'baz=qux'
+  ])
 })
diff --git a/test/util.js b/test/util.js
index 48a21a1141f..794c68e3f77 100644
--- a/test/util.js
+++ b/test/util.js
@@ -83,12 +83,13 @@ test('validateHandler', (t) => {
 })
 
 test('parseHeaders', (t) => {
-  t.plan(5)
+  t.plan(6)
   t.same(util.parseHeaders(['key', 'value']), { key: 'value' })
   t.same(util.parseHeaders([Buffer.from('key'), Buffer.from('value')]), { key: 'value' })
   t.same(util.parseHeaders(['Key', 'Value']), { key: 'Value' })
   t.same(util.parseHeaders(['Key', 'value', 'key', 'Value']), { key: ['value', 'Value'] })
   t.same(util.parseHeaders(['key', ['value1', 'value2', 'value3']]), { key: ['value1', 'value2', 'value3'] })
+  t.same(util.parseHeaders([Buffer.from('key'), [Buffer.from('value1'), Buffer.from('value2'), Buffer.from('value3')]]), { key: ['value1', 'value2', 'value3'] })
 })
 
 test('parseRawHeaders', (t) => {