diff --git a/include/common/h2.h b/include/common/h2.h
index c434ed9..9b9684d 100644
--- a/include/common/h2.h
+++ b/include/common/h2.h
@@ -177,6 +177,7 @@
 #define H2_MSGF_BODY           0x0001    // a body is present
 #define H2_MSGF_BODY_CL        0x0002    // content-length is present
 #define H2_MSGF_BODY_TUNNEL    0x0004    // a tunnel is in use (CONNECT)
+#define H2_MSGF_RSP_1XX        0x0010    // a 1xx ( != 101) HEADERS frame was received
 
 #define H2_MAX_STREAM_ID       ((1U << 31) - 1)
 #define H2_MAX_FRAME_LEN       ((1U << 24) - 1)