diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index d882a8288..f3a9b9d2c 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -4242,11 +4242,14 @@ static size_t fcgi_snd_buf(struct stconn *sc, struct buffer *buf, size_t count,
 
   done:
 	if (fstrm->state >= FCGI_SS_HLOC) {
+		struct htx_ret htxret;
+
 		/* trim any possibly pending data after we close (extra CR-LF,
 		 * unprocessed trailers, abnormal extra data, ...)
 		 */
-		total += count;
-		count = 0;
+		htxret = htx_drain(htx, count);
+		total += htxret.ret;
+		count -= htxret.ret;
 	}
 
 	if (fstrm->state == FCGI_SS_ERROR) {