diff --git a/lib/_http_outgoing.js b/lib/_http_outgoing.js
index b62dea4a24dd2f..770e555d1ead8a 100644
--- a/lib/_http_outgoing.js
+++ b/lib/_http_outgoing.js
@@ -52,30 +52,14 @@ const { utcDate } = internalHttp;
 
 const kIsCorked = Symbol('isCorked');
 
-var RE_FIELDS =
-  /^(?:Connection|Transfer-Encoding|Content-Length|Date|Expect|Trailer|Upgrade)$/i;
-var RE_CONN_VALUES = /(?:^|\W)close|upgrade(?:$|\W)/ig;
+var RE_CONN_CLOSE = /(?:^|\W)close(?:$|\W)/i;
 var RE_TE_CHUNKED = common.chunkExpression;
 
 // isCookieField performs a case-insensitive comparison of a provided string
-// against the word "cookie." This method (at least as of V8 5.4) is faster than
-// the equivalent case-insensitive regexp, even if isCookieField does not get
-// inlined.
+// against the word "cookie." As of V8 6.6 this is faster than handrolling or
+// using a case-insensitive RegExp.
 function isCookieField(s) {
-  if (s.length !== 6) return false;
-  var ch = s.charCodeAt(0);
-  if (ch !== 99 && ch !== 67) return false;
-  ch = s.charCodeAt(1);
-  if (ch !== 111 && ch !== 79) return false;
-  ch = s.charCodeAt(2);
-  if (ch !== 111 && ch !== 79) return false;
-  ch = s.charCodeAt(3);
-  if (ch !== 107 && ch !== 75) return false;
-  ch = s.charCodeAt(4);
-  if (ch !== 105 && ch !== 73) return false;
-  ch = s.charCodeAt(5);
-  if (ch !== 101 && ch !== 69) return false;
-  return true;
+  return s.length === 6 && s.toLowerCase() === 'cookie';
 }
 
 function noopPendingOutput(amount) {}
@@ -448,43 +432,31 @@ function storeHeader(self, state, key, value, validate) {
   matchHeader(self, state, key, value);
 }
 
-function matchConnValue(self, state, value) {
-  var sawClose = false;
-  var m = RE_CONN_VALUES.exec(value);
-  while (m) {
-    if (m[0].length === 5)
-      sawClose = true;
-    m = RE_CONN_VALUES.exec(value);
-  }
-  if (sawClose)
-    self._last = true;
-  else
-    self.shouldKeepAlive = true;
-}
-
 function matchHeader(self, state, field, value) {
-  var m = RE_FIELDS.exec(field);
-  if (!m)
+  if (field.length < 4 || field.length > 17)
     return;
-  var len = m[0].length;
-  if (len === 10) {
-    state.connection = true;
-    matchConnValue(self, state, value);
-  } else if (len === 17) {
-    state.te = true;
-    if (RE_TE_CHUNKED.test(value)) self.chunkedEncoding = true;
-  } else if (len === 14) {
-    state.contLen = true;
-  } else if (len === 4) {
-    state.date = true;
-  } else if (len === 6) {
-    state.expect = true;
-  } else if (len === 7) {
-    var ch = m[0].charCodeAt(0);
-    if (ch === 85 || ch === 117)
-      state.upgrade = true;
-    else
-      state.trailer = true;
+  field = field.toLowerCase();
+  switch (field) {
+    case 'connection':
+      state.connection = true;
+      if (RE_CONN_CLOSE.test(value))
+        self._last = true;
+      else
+        self.shouldKeepAlive = true;
+      break;
+    case 'transfer-encoding':
+      state.te = true;
+      if (RE_TE_CHUNKED.test(value)) self.chunkedEncoding = true;
+      break;
+    case 'content-length':
+      state.contLen = true;
+      break;
+    case 'date':
+    case 'expect':
+    case 'trailer':
+    case 'upgrade':
+      state[field] = true;
+      break;
   }
 }