diff --git a/Release/include/cpprest/details/http_constants.dat b/Release/include/cpprest/details/http_constants.dat
index f2bd531be5..f3d051f236 100644
--- a/Release/include/cpprest/details/http_constants.dat
+++ b/Release/include/cpprest/details/http_constants.dat
@@ -21,6 +21,9 @@ DAT(NonAuthInfo,           203, _XPLATSTR("Non-Authoritative Information"))
 DAT(NoContent,             204, _XPLATSTR("No Content"))
 DAT(ResetContent,          205, _XPLATSTR("Reset Content"))
 DAT(PartialContent,        206, _XPLATSTR("Partial Content"))
+DAT(MultiStatus,           207, _XPLATSTR("Multi-Status"))
+DAT(AlreadyReported,       208, _XPLATSTR("Already Reported"))
+DAT(IMUsed,                226, _XPLATSTR("IM Used"))
 DAT(MultipleChoices,       300, _XPLATSTR("Multiple Choices"))
 DAT(MovedPermanently,      301, _XPLATSTR("Moved Permanently"))
 DAT(Found,                 302, _XPLATSTR("Found"))
@@ -47,13 +50,26 @@ DAT(RequestUriTooLarge,    414, _XPLATSTR("Request Uri Too Large"))
 DAT(UnsupportedMediaType,  415, _XPLATSTR("Unsupported Media Type"))
 DAT(RangeNotSatisfiable,   416, _XPLATSTR("Requested range not satisfiable"))
 DAT(ExpectationFailed,     417, _XPLATSTR("Expectation Failed"))
+DAT(MisdirectedRequest,    421, _XPLATSTR("Misdirected Request"))
+DAT(UnprocessableEntity,   422, _XPLATSTR(Unprocessable Entity"))
+DAT(Locked,                423, _XPLATSTR(Locked"))
+DAT(FailedDependency,      424, _XPLATSTR(Failed Dependency"))
+DAT(UpgradeRequired,       426, _XPLATSTR(Upgrade Required"))
+DAT(PreconditionRequired,  428, _XPLATSTR(Precondition Required"))
 DAT(TooManyRequests,       429, _XPLATSTR("Too Many Requests"))
+DAT(RequestHeaderFieldsTooLarge,  431, _XPLATSTR("Request Header Fields Too Large"))
+DAT(UnavailableForLegalReasons,   451, _XPLATSTR("Unavailable For Legal Reasons"))
 DAT(InternalError,         500, _XPLATSTR("Internal Error"))
 DAT(NotImplemented,        501, _XPLATSTR("Not Implemented"))
 DAT(BadGateway,            502, _XPLATSTR("Bad Gateway"))
 DAT(ServiceUnavailable,    503, _XPLATSTR("Service Unavailable"))
 DAT(GatewayTimeout,        504, _XPLATSTR("Gateway Time-out"))
 DAT(HttpVersionNotSupported, 505, _XPLATSTR("HTTP Version not supported"))
+DAT(VariantAlsoNegotiates, 506, _XPLATSTR("Variant Also Negotiates"))
+DAT(InsufficientStorage,   507, _XPLATSTR("Insufficient Storage"))
+DAT(LoopDetected,          508, _XPLATSTR("Loop Detected"))
+DAT(NotExtended,           510, _XPLATSTR("Not Extended"))
+DAT(NetworkAuthenticationRequired, 511, _XPLATSTR("Network Authentication Required"))
 #endif // _PHRASES
 
 #ifdef _HEADER_NAMES