diff --git a/akka-http-core/src/main/scala/akka/http/model/parser/CommonRules.scala b/akka-http-core/src/main/scala/akka/http/model/parser/CommonRules.scala
index 3a037546af..e42fea003b 100644
--- a/akka-http-core/src/main/scala/akka/http/model/parser/CommonRules.scala
+++ b/akka-http-core/src/main/scala/akka/http/model/parser/CommonRules.scala
@@ -71,13 +71,13 @@ private[parser] trait CommonRules { this: Parser with StringBuilding ⇒
   }
 
   def `IMF-fixdate` = rule { // mixture of the spec-ed `IMF-fixdate` and `rfc850-date`
-    (`day-name` | `day-name-l`) ~ ", " ~ (date1 | date2) ~ ' ' ~ `time-of-day` ~ ' ' ~ ("GMT" | "UTC") ~> {
+    (`day-name-l` | `day-name`) ~ ", " ~ (date1 | date2) ~ ' ' ~ `time-of-day` ~ ' ' ~ ("GMT" | "UTC") ~> {
       (wkday, day, month, year, hour, min, sec) ⇒ createDateTime(year, month, day, hour, min, sec, wkday)
     }
   }
 
   def `day-name` = rule(
-    "Mon" ~ push(1) | "Tue" ~ push(2) | "Wed" ~ push(3) | "Thu" ~ push(4) | "Fri" ~ push(5) | "Sat" ~ push(6) | "Sun" ~ push(7))
+    "Sun" ~ push(0) | "Mon" ~ push(1) | "Tue" ~ push(2) | "Wed" ~ push(3) | "Thu" ~ push(4) | "Fri" ~ push(5) | "Sat" ~ push(6))
 
   def date1 = rule { day ~ ' ' ~ month ~ ' ' ~ year }
 
@@ -101,8 +101,8 @@ private[parser] trait CommonRules { this: Parser with StringBuilding ⇒
   def date2 = rule { day ~ '-' ~ month ~ '-' ~ digit2 }
 
   def `day-name-l` = rule(
-    "Monday" ~ push(1) | "Tuesday" ~ push(2) | "Wednesday" ~ push(3) | "Thursday" ~ push(4) | "Friday" ~ push(5) |
-      "Saturday" ~ push(6) | "Sunday" ~ push(7))
+    "Sunday" ~ push(0) | "Monday" ~ push(1) | "Tuesday" ~ push(2) | "Wednesday" ~ push(3) | "Thursday" ~ push(4) |
+      "Friday" ~ push(5) | "Saturday" ~ push(6))
 
   def `asctime-date` = rule {
     `day-name` ~ ' ' ~ date3 ~ ' ' ~ `time-of-day` ~ ' ' ~ year ~> {
@@ -269,7 +269,13 @@ private[parser] trait CommonRules { this: Parser with StringBuilding ⇒
 
   // http://www.rfc-editor.org/errata_search.php?rfc=6265
   def `extension-av` = rule {
-    capture(zeroOrMore(`av-octet`)) ~ OWS ~> { (c: HttpCookie, s: String) ⇒ c.copy(extension = Some(s)) }
+    !(ignoreCase("expires=")
+      | ignoreCase("max-age=")
+      | ignoreCase("domain=")
+      | ignoreCase("path=")
+      | ignoreCase("secure")
+      | ignoreCase("httponly")) ~
+      capture(zeroOrMore(`av-octet`)) ~ OWS ~> { (c: HttpCookie, s: String) ⇒ c.copy(extension = Some(s)) }
   }
 
   // ******************************************************************************************
diff --git a/akka-http-core/src/test/scala/akka/http/model/parser/HttpHeaderSpec.scala b/akka-http-core/src/test/scala/akka/http/model/parser/HttpHeaderSpec.scala
index 2e05d80ca0..e3a5424457 100644
--- a/akka-http-core/src/test/scala/akka/http/model/parser/HttpHeaderSpec.scala
+++ b/akka-http-core/src/test/scala/akka/http/model/parser/HttpHeaderSpec.scala
@@ -361,6 +361,65 @@ class HttpHeaderSpec extends FreeSpec with Matchers {
         `Set-Cookie`(HttpCookie("foo", "bar", domain = Some("example.com"), path = Some("/this is a path with blanks"),
           extension = Some("extension with blanks"))).renderedTo(
           "foo=bar; Domain=example.com; Path=/this is a path with blanks; extension with blanks")
+
+      // test all weekdays
+      "Set-Cookie: lang=; Expires=Sun, 07 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 7, 0, 42, 55)), maxAge = Some(12345)))
+      "Set-Cookie: lang=; Expires=Sunday, 07 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 7, 0, 42, 55)), maxAge = Some(12345)))
+        .renderedTo("lang=; Expires=Sun, 07 Dec 2014 00:42:55 GMT; Max-Age=12345")
+
+      "Set-Cookie: lang=; Expires=Mon, 08 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 8, 0, 42, 55)), maxAge = Some(12345)))
+      "Set-Cookie: lang=; Expires=Monday, 08 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 8, 0, 42, 55)), maxAge = Some(12345)))
+        .renderedTo("lang=; Expires=Mon, 08 Dec 2014 00:42:55 GMT; Max-Age=12345")
+
+      "Set-Cookie: lang=; Expires=Tue, 09 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 9, 0, 42, 55)), maxAge = Some(12345)))
+      "Set-Cookie: lang=; Expires=Tuesday, 09 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 9, 0, 42, 55)), maxAge = Some(12345)))
+        .renderedTo("lang=; Expires=Tue, 09 Dec 2014 00:42:55 GMT; Max-Age=12345")
+
+      "Set-Cookie: lang=; Expires=Wed, 10 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 10, 0, 42, 55)), maxAge = Some(12345)))
+      "Set-Cookie: lang=; Expires=Wednesday, 10 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 10, 0, 42, 55)), maxAge = Some(12345)))
+        .renderedTo("lang=; Expires=Wed, 10 Dec 2014 00:42:55 GMT; Max-Age=12345")
+
+      "Set-Cookie: lang=; Expires=Thu, 11 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 11, 0, 42, 55)), maxAge = Some(12345)))
+      "Set-Cookie: lang=; Expires=Thursday, 11 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 11, 0, 42, 55)), maxAge = Some(12345)))
+        .renderedTo("lang=; Expires=Thu, 11 Dec 2014 00:42:55 GMT; Max-Age=12345")
+
+      "Set-Cookie: lang=; Expires=Fri, 12 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 12, 0, 42, 55)), maxAge = Some(12345)))
+      "Set-Cookie: lang=; Expires=Friday, 12 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 12, 0, 42, 55)), maxAge = Some(12345)))
+        .renderedTo("lang=; Expires=Fri, 12 Dec 2014 00:42:55 GMT; Max-Age=12345")
+
+      "Set-Cookie: lang=; Expires=Sat, 13 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 13, 0, 42, 55)), maxAge = Some(12345)))
+      "Set-Cookie: lang=; Expires=Saturday, 13 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        `Set-Cookie`(HttpCookie("lang", "", expires = Some(DateTime(2014, 12, 13, 0, 42, 55)), maxAge = Some(12345)))
+        .renderedTo("lang=; Expires=Sat, 13 Dec 2014 00:42:55 GMT; Max-Age=12345")
+
+      "Set-Cookie: lang=; Expires=Mon, 13 Dec 2014 00:42:55 GMT; Max-Age=12345" =!=
+        ErrorInfo("Illegal HTTP header 'Set-Cookie': Illegal weekday in date 2014-12-13T00:42:55", "is 'Mon' but should be 'Sat'")
+
+      "Set-Cookie: lang=; Expires=xxxx" =!=
+        ErrorInfo(
+          "Illegal HTTP header 'Set-Cookie': Invalid input 'x', expected '\\r', WSP, 'S', 'M', 'T', 'W', 'F' or '0' (line 1, column 16)",
+          "lang=; Expires=xxxx\n               ^")
+
+      // extra examples from play
+      "Set-Cookie: PLAY_FLASH=\"success=found\"; Path=/; HTTPOnly" =!=
+        `Set-Cookie`(HttpCookie("PLAY_FLASH", "success=found", path = Some("/"), httpOnly = true))
+        .renderedTo("PLAY_FLASH=success=found; Path=/; HttpOnly")
+      "Set-Cookie: PLAY_FLASH=; Expires=Sun, 07 Dec 2014 22:48:47 GMT; Path=/; HTTPOnly" =!=
+        `Set-Cookie`(HttpCookie("PLAY_FLASH", "", expires = Some(DateTime(2014, 12, 7, 22, 48, 47)), path = Some("/"), httpOnly = true))
+        .renderedTo("PLAY_FLASH=; Expires=Sun, 07 Dec 2014 22:48:47 GMT; Path=/; HttpOnly")
     }
 
     "User-Agent" in {