diff --git a/src/mux_h2.c b/src/mux_h2.c
index 49303a5f2..c83230a35 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -4096,6 +4096,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
 		outbuf.area[outbuf.data++] = 0x42; // indexed name -- name=":method" (idx 2)
 		outbuf.area[outbuf.data++] = meth.len; // method length
 		memcpy(&outbuf.area[outbuf.data], meth.ptr, meth.len);
+		outbuf.data += meth.len;
 	}
 	else {
 		if (b_space_wraps(&h2c->mbuf))