diff --git a/doc/management.txt b/doc/management.txt
index 2600478fd..f77ed4c1b 100644
--- a/doc/management.txt
+++ b/doc/management.txt
@@ -2126,7 +2126,10 @@ show fd [<fd>]
   listener's state and its frontend are reported. There is no point in using
   this command without a good knowledge of the internals. It's worth noting
   that the output format may evolve over time so this output must not be parsed
-  by tools designed to be durable.
+  by tools designed to be durable. Some internal structure states may look
+  suspicious to the function listing them, in this case the output line will be
+  suffixed with an exclamation mark ('!'). This may help find a starting point
+  when trying to diagnose an incident.
 
 show info [typed|json] [desc]
   Dump info about haproxy status on current process. If "typed" is passed as an
diff --git a/include/haproxy/connection-t.h b/include/haproxy/connection-t.h
index 7dd3d15d9..62bb81441 100644
--- a/include/haproxy/connection-t.h
+++ b/include/haproxy/connection-t.h
@@ -381,7 +381,7 @@ struct xprt_ops {
 	int (*unsubscribe)(struct connection *conn, void *xprt_ctx, int event_type, struct wait_event *es); /* Unsubscribe <es> from events */
 	int (*remove_xprt)(struct connection *conn, void *xprt_ctx, void *toremove_ctx, const struct xprt_ops *newops, void *newctx); /* Remove an xprt from the connection, used by temporary xprt such as the handshake one */
 	int (*add_xprt)(struct connection *conn, void *xprt_ctx, void *toadd_ctx, const struct xprt_ops *toadd_ops, void **oldxprt_ctx, const struct xprt_ops **oldxprt_ops); /* Add a new XPRT as the new xprt, and return the old one */
-	void (*show_fd)(struct buffer *, const struct connection *, const void *ctx); /* append some data about xprt for "show fd" */
+	int (*show_fd)(struct buffer *, const struct connection *, const void *ctx); /* append some data about xprt for "show fd"; returns non-zero if suspicious */
 };
 
 /* mux_ops describes the mux operations, which are to be performed at the
@@ -404,7 +404,7 @@ struct mux_ops {
 	struct conn_stream *(*attach)(struct connection *, struct session *sess); /* Create and attach a conn_stream to an outgoing connection */
 	const struct conn_stream *(*get_first_cs)(const struct connection *); /* retrieves any valid conn_stream from this connection */
 	void (*detach)(struct conn_stream *); /* Detach a conn_stream from an outgoing connection, when the request is done */
-	void (*show_fd)(struct buffer *, struct connection *); /* append some data about connection into chunk for "show fd" */
+	int (*show_fd)(struct buffer *, struct connection *); /* append some data about connection into chunk for "show fd"; returns non-zero if suspicious */
 	int (*subscribe)(struct conn_stream *cs, int event_type,  struct wait_event *es); /* Subscribe <es> to events, such as "being able to send" */
 	int (*unsubscribe)(struct conn_stream *cs, int event_type,  struct wait_event *es); /* Unsubscribe <es> from events */
 	int (*avail_streams)(struct connection *conn); /* Returns the number of streams still available for a connection */
diff --git a/src/cli.c b/src/cli.c
index 060372988..ab5fe9a15 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -1037,6 +1037,7 @@ static int cli_io_handler_show_fd(struct appctx *appctx)
 		const void *xprt_ctx = NULL;
 		uint32_t conn_flags = 0;
 		int is_back = 0;
+		int suspicious = 0;
 
 		fdt = fdtab[fd];
 
@@ -1100,7 +1101,7 @@ static int cli_io_handler_show_fd(struct appctx *appctx)
 			if (mux) {
 				chunk_appendf(&trash, " mux=%s ctx=%p", mux->name, ctx);
 				if (mux->show_fd)
-					mux->show_fd(&trash, fdt.owner);
+					suspicious |= mux->show_fd(&trash, fdt.owner);
 			}
 			else
 				chunk_appendf(&trash, " nomux");
@@ -1110,7 +1111,7 @@ static int cli_io_handler_show_fd(struct appctx *appctx)
 				if (xprt_ctx || xprt->show_fd)
 					chunk_appendf(&trash, " xprt_ctx=%p", xprt_ctx);
 				if (xprt->show_fd)
-					xprt->show_fd(&trash, conn, xprt_ctx);
+					suspicious |= xprt->show_fd(&trash, conn, xprt_ctx);
 			}
 		}
 		else if (fdt.iocb == sock_accept_iocb) {
@@ -1124,7 +1125,7 @@ static int cli_io_handler_show_fd(struct appctx *appctx)
 #ifdef DEBUG_FD
 		chunk_appendf(&trash, " evcnt=%u", fdtab[fd].event_count);
 #endif
-		chunk_appendf(&trash, "\n");
+		chunk_appendf(&trash, "%s\n", suspicious ? " !" : "");
 
 		if (ci_putchk(si_ic(si), &trash) == -1) {
 			si_rx_room_blk(si);
diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index 4e2f0cced..765cff3b8 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -4053,7 +4053,7 @@ static size_t fcgi_snd_buf(struct conn_stream *cs, struct buffer *buf, size_t co
 }
 
 /* for debugging with CLI's "show fd" command */
-static void fcgi_show_fd(struct buffer *msg, struct connection *conn)
+static int fcgi_show_fd(struct buffer *msg, struct connection *conn)
 {
 	struct fcgi_conn *fconn = conn->ctx;
 	struct fcgi_strm *fstrm = NULL;
@@ -4064,7 +4064,7 @@ static void fcgi_show_fd(struct buffer *msg, struct connection *conn)
 	struct buffer *hmbuf, *tmbuf;
 
 	if (!fconn)
-		return;
+		return 0;
 
 	list_for_each_entry(fstrm, &fconn->send_list, send_list)
 		send_cnt++;
@@ -4116,6 +4116,7 @@ static void fcgi_show_fd(struct buffer *msg, struct connection *conn)
 			}
 		}
 	}
+	return 0;
 }
 
 /* Migrate the the connection to the current thread.
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 4a4b5edc4..ae50a5ef9 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -3141,7 +3141,7 @@ static int h1_ctl(struct connection *conn, enum mux_ctl_type mux_ctl, void *outp
 }
 
 /* for debugging with CLI's "show fd" command */
-static void h1_show_fd(struct buffer *msg, struct connection *conn)
+static int h1_show_fd(struct buffer *msg, struct connection *conn)
 {
 	struct h1c *h1c = conn->ctx;
 	struct h1s *h1s = h1c->h1s;
@@ -3181,6 +3181,7 @@ static void h1_show_fd(struct buffer *msg, struct connection *conn)
 			}
 		}
 	}
+	return 0;
 }
 
 
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 0a4a62af5..2fbf19675 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -6192,7 +6192,7 @@ static size_t h2_snd_buf(struct conn_stream *cs, struct buffer *buf, size_t coun
 }
 
 /* for debugging with CLI's "show fd" command */
-static void h2_show_fd(struct buffer *msg, struct connection *conn)
+static int h2_show_fd(struct buffer *msg, struct connection *conn)
 {
 	struct h2c *h2c = conn->ctx;
 	struct h2s *h2s = NULL;
@@ -6204,7 +6204,7 @@ static void h2_show_fd(struct buffer *msg, struct connection *conn)
 	struct buffer *hmbuf, *tmbuf;
 
 	if (!h2c)
-		return;
+		return 0;
 
 	list_for_each_entry(h2s, &h2c->fctl_list, list)
 		fctl_cnt++;
@@ -6262,6 +6262,7 @@ static void h2_show_fd(struct buffer *msg, struct connection *conn)
 			}
 		}
 	}
+	return 0;
 }
 
 /* Migrate the the connection to the current thread.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 483662ec2..ca8dcc63c 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -6354,12 +6354,12 @@ static int ssl_check_async_engine_count(void) {
 /* "show fd" helper to dump ssl internals. Warning: the output buffer is often
  * the common trash!
  */
-static void ssl_sock_show_fd(struct buffer *buf, const struct connection *conn, const void *ctx)
+static int ssl_sock_show_fd(struct buffer *buf, const struct connection *conn, const void *ctx)
 {
 	const struct ssl_sock_ctx *sctx = ctx;
 
 	if (!sctx)
-		return;
+		return 0;
 
 	if (sctx->conn != conn)
 		chunk_appendf(&trash, " xctx.conn=%p(BOGUS!)", sctx->conn);
@@ -6383,6 +6383,7 @@ static void ssl_sock_show_fd(struct buffer *buf, const struct connection *conn,
 	}
 	chunk_appendf(&trash, " .sent_early=%d", sctx->sent_early_data);
 	chunk_appendf(&trash, " .early_in=%d", (int)sctx->early_buf.data);
+	return 0;
 }
 
 #if (defined SSL_CTRL_SET_TLSEXT_TICKET_KEY_CB && TLS_TICKETS_NO > 0)