diff --git a/include/haproxy/connection-t.h b/include/haproxy/connection-t.h
index cf1a4cb6a..3c0693883 100644
--- a/include/haproxy/connection-t.h
+++ b/include/haproxy/connection-t.h
@@ -424,7 +424,7 @@ struct mux_ops {
 	size_t (*rcv_buf)(struct stconn *sc, struct buffer *buf, size_t count, int flags); /* Called from the upper layer to get data */
 	size_t (*snd_buf)(struct stconn *sc, struct buffer *buf, size_t count, int flags); /* Called from the upper layer to send data */
 	size_t (*nego_fastfwd)(struct stconn *sc, struct buffer *input, size_t count, unsigned int may_splice); /* Callback to fill the SD iobuf */
-	void (*done_fastfwd)(struct stconn *sc); /* Callback to terminate fast data forwarding */
+	size_t (*done_fastfwd)(struct stconn *sc); /* Callback to terminate fast data forwarding */
 	int (*fastfwd)(struct stconn *sc, unsigned int count, unsigned int flags); /* Callback to init fast data forwarding */
 	int (*resume_fastfwd)(struct stconn *sc, unsigned int flags); /* Callback to resume fast data forwarding */
 	void (*shutr)(struct stconn *sc, enum co_shr_mode);     /* shutr function */
diff --git a/include/haproxy/stconn.h b/include/haproxy/stconn.h
index 71751f697..4ba6aca20 100644
--- a/include/haproxy/stconn.h
+++ b/include/haproxy/stconn.h
@@ -132,41 +132,6 @@ static inline size_t se_ff_data(struct sedesc *se)
 	return (se->iobuf.data + (se->iobuf.pipe ? se->iobuf.pipe->data : 0));
 }
 
-static inline size_t se_nego_ff(struct sedesc *se, struct buffer *input, size_t count, unsigned int may_splice)
-{
-	size_t ret = 0;
-
-	if (se_fl_test(se, SE_FL_T_MUX)) {
-		const struct mux_ops *mux = se->conn->mux;
-
-		se->iobuf.flags &= ~IOBUF_FL_FF_BLOCKED;
-		if (mux->nego_fastfwd && mux->done_fastfwd) {
-			ret = mux->nego_fastfwd(se->sc, input, count, may_splice);
-			if ((se->iobuf.flags & IOBUF_FL_FF_BLOCKED) && !(se->sc->wait_event.events & SUB_RETRY_SEND)) {
-				/* The SC must be subs for send to be notify when some
-				 * space is made
-				 */
-				mux->subscribe(se->sc, SUB_RETRY_SEND, &se->sc->wait_event);
-			}
-			goto end;
-		}
-	}
-	se->iobuf.flags |= IOBUF_FL_NO_FF;
-
-  end:
-	return ret;
-}
-
-static inline void se_done_ff(struct sedesc *se)
-{
-	if (se_fl_test(se, SE_FL_T_MUX)) {
-		const struct mux_ops *mux = se->conn->mux;
-
-		BUG_ON(!mux->done_fastfwd);
-		mux->done_fastfwd(se->sc);
-	}
-}
-
 /* stream connector version */
 static forceinline void sc_ep_zero(struct stconn *sc)
 {
@@ -544,4 +509,45 @@ static inline void se_need_more_data(struct sedesc *se)
 	se_fl_set(se, SE_FL_WAIT_DATA);
 }
 
+
+static inline size_t se_nego_ff(struct sedesc *se, struct buffer *input, size_t count, unsigned int may_splice)
+{
+	size_t ret = 0;
+
+	if (se_fl_test(se, SE_FL_T_MUX)) {
+		const struct mux_ops *mux = se->conn->mux;
+
+		se->iobuf.flags &= ~IOBUF_FL_FF_BLOCKED;
+		if (mux->nego_fastfwd && mux->done_fastfwd) {
+			ret = mux->nego_fastfwd(se->sc, input, count, may_splice);
+			if ((se->iobuf.flags & IOBUF_FL_FF_BLOCKED) && !(se->sc->wait_event.events & SUB_RETRY_SEND)) {
+				/* The SC must be subs for send to be notify when some
+				 * space is made
+				 */
+				mux->subscribe(se->sc, SUB_RETRY_SEND, &se->sc->wait_event);
+			}
+			goto end;
+		}
+	}
+	se->iobuf.flags |= IOBUF_FL_NO_FF;
+
+  end:
+	return ret;
+}
+
+static inline void se_done_ff(struct sedesc *se)
+{
+	if (se_fl_test(se, SE_FL_T_MUX)) {
+		const struct mux_ops *mux = se->conn->mux;
+		size_t sent, to_send = se_ff_data(se);
+
+		BUG_ON(!mux->done_fastfwd);
+		sent = mux->done_fastfwd(se->sc);
+		if (sent > 0)
+			sc_ep_report_send_activity(se->sc);
+		else if (to_send > 0) /* implies sent == 0 */
+			sc_ep_report_blocked_send(se->sc);
+	}
+}
+
 #endif /* _HAPROXY_STCONN_H */
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 7dc424edb..4477c5a16 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -4479,7 +4479,7 @@ static size_t h1_nego_ff(struct stconn *sc, struct buffer *input, size_t count,
 	return ret;
 }
 
-static void h1_done_ff(struct stconn *sc)
+static size_t h1_done_ff(struct stconn *sc)
 {
 	struct h1s *h1s = __sc_mux_strm(sc);
 	struct h1c *h1c = h1s->h1c;
@@ -4546,6 +4546,7 @@ static void h1_done_ff(struct stconn *sc)
 	}
 
 	TRACE_LEAVE(H1_EV_STRM_RECV, h1c->conn, h1s, 0, (size_t[]){total});
+	return total;
 }
 
 static int h1_fastfwd(struct stconn *sc, unsigned int count, unsigned int flags)
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 95003cfb3..98b796b81 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -7023,13 +7023,14 @@ static size_t h2_nego_ff(struct stconn *sc, struct buffer *input, size_t count,
 	return ret;
 }
 
-static void h2_done_ff(struct stconn *sc)
+static size_t h2_done_ff(struct stconn *sc)
 {
 	struct h2s *h2s = __sc_mux_strm(sc);
 	struct h2c *h2c = h2s->h2c;
 	struct sedesc *sd = h2s->sd;
 	struct buffer *mbuf;
 	char *head;
+	size_t total = 0;
 
 	TRACE_ENTER(H2_EV_H2S_SEND|H2_EV_STRM_SEND, h2s->h2c->conn, h2s);
 
@@ -7067,10 +7068,11 @@ static void h2_done_ff(struct stconn *sc)
 	/* Perform a synchronous send but in all cases, consider
 	 * everything was already sent from the SC point of view.
 	 */
-	h2_set_frame_size(head, sd->iobuf.data);
+	total = sd->iobuf.data;
+	h2_set_frame_size(head, total);
 	b_add(mbuf, 9);
-	h2s->sws -= sd->iobuf.data;
-	h2c->mws -= sd->iobuf.data;
+	h2s->sws -= total;
+	h2c->mws -= total;
 	if (h2_send(h2s->h2c))
 		tasklet_wakeup(h2s->h2c->wait_event.tasklet);
 
@@ -7080,6 +7082,7 @@ static void h2_done_ff(struct stconn *sc)
 	sd->iobuf.data = 0;
 
 	TRACE_LEAVE(H2_EV_H2S_SEND|H2_EV_STRM_SEND, h2s->h2c->conn, h2s);
+	return total;
 }
 
 static int h2_resume_ff(struct stconn *sc, unsigned int flags)
diff --git a/src/mux_pt.c b/src/mux_pt.c
index 52a5527d9..802aa4c8a 100644
--- a/src/mux_pt.c
+++ b/src/mux_pt.c
@@ -612,7 +612,7 @@ static size_t mux_pt_nego_ff(struct stconn *sc, struct buffer *input, size_t cou
 	return ret;
 }
 
-static void mux_pt_done_ff(struct stconn *sc)
+static size_t mux_pt_done_ff(struct stconn *sc)
 {
 	struct connection *conn = __sc_conn(sc);
 	struct mux_pt_ctx *ctx = conn->ctx;
@@ -641,6 +641,7 @@ static void mux_pt_done_ff(struct stconn *sc)
 	}
 
 	TRACE_LEAVE(PT_EV_TX_DATA, conn, sc, 0, (size_t[]){total});
+	return total;
 }
 
 static int mux_pt_fastfwd(struct stconn *sc, unsigned int count, unsigned int flags)