diff --git a/libraries/ESP8266WebServer/keywords.txt b/libraries/ESP8266WebServer/keywords.txt
index 22e3d74e4..4f35e1ffe 100644
--- a/libraries/ESP8266WebServer/keywords.txt
+++ b/libraries/ESP8266WebServer/keywords.txt
@@ -34,3 +34,4 @@ onNotFound	KEYWORD2
 HTTP_GET	LITERAL1
 HTTP_POST	LITERAL1
 HTTP_ANY	LITERAL1
+CONTENT_LENGTH_UNKNOWN	LITERAL1