diff --git a/mitmproxy/net/http/status_codes.py b/mitmproxy/net/http/status_codes.py
index 5a83cd73f..7e826e0bc 100644
--- a/mitmproxy/net/http/status_codes.py
+++ b/mitmproxy/net/http/status_codes.py
@@ -36,6 +36,7 @@ UNSUPPORTED_MEDIA_TYPE = 415
 REQUESTED_RANGE_NOT_SATISFIABLE = 416
 EXPECTATION_FAILED = 417
 IM_A_TEAPOT = 418
+CLIENT_CLOSED_REQUEST = 499
 
 INTERNAL_SERVER_ERROR = 500
 NOT_IMPLEMENTED = 501
@@ -91,6 +92,7 @@ RESPONSES = {
     REQUESTED_RANGE_NOT_SATISFIABLE: "Requested Range not satisfiable",
     EXPECTATION_FAILED: "Expectation Failed",
     IM_A_TEAPOT: "I'm a teapot",
+    CLIENT_CLOSED_REQUEST: "Client Closed Request",
 
     # 500
     INTERNAL_SERVER_ERROR: "Internal Server Error",