diff --git a/include/winhttp.h b/include/winhttp.h
index dab9bbaa7b9..4c647683dfe 100644
--- a/include/winhttp.h
+++ b/include/winhttp.h
@@ -436,6 +436,7 @@ typedef int INTERNET_SCHEME, *LPINTERNET_SCHEME;
 #define WINHTTP_AUTH_TARGET_SERVER     0x00000000
 #define WINHTTP_AUTH_TARGET_PROXY      0x00000001
 
+#define WINHTTP_TIME_FORMAT_BUFSIZE    62
 
 typedef struct
 {