diff --git a/include/haproxy/connection.h b/include/haproxy/connection.h
index d759238b2..d796991b4 100644
--- a/include/haproxy/connection.h
+++ b/include/haproxy/connection.h
@@ -84,7 +84,7 @@ int conn_install_mux_be(struct connection *conn, void *ctx, struct session *sess
                         const struct mux_ops *force_mux_ops);
 int conn_install_mux_chk(struct connection *conn, void *ctx, struct session *sess);
 
-void conn_delete_from_tree(struct connection *conn);
+void conn_delete_from_tree(struct connection *conn, int thr);
 
 void conn_init(struct connection *conn, void *target);
 struct connection *conn_new(void *target);
diff --git a/src/backend.c b/src/backend.c
index a835be5a1..ea3440c37 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1313,7 +1313,7 @@ struct connection *conn_backend_get(int reuse_mode,
 	HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 	conn = srv_lookup_conn(is_safe ? &srv->per_thr[tid].safe_conns : &srv->per_thr[tid].idle_conns, hash);
 	if (conn)
-		conn_delete_from_tree(conn);
+		conn_delete_from_tree(conn, tid);
 
 	/* If we failed to pick a connection from the idle list, let's try again with
 	 * the safe list.
@@ -1321,7 +1321,7 @@ struct connection *conn_backend_get(int reuse_mode,
 	if (!conn && !is_safe && srv->curr_safe_nb > 0) {
 		conn = srv_lookup_conn(&srv->per_thr[tid].safe_conns, hash);
 		if (conn) {
-			conn_delete_from_tree(conn);
+			conn_delete_from_tree(conn, tid);
 			is_safe = 1;
 		}
 	}
@@ -1382,7 +1382,7 @@ check_tgid:
 			conn = srv_lookup_conn(tree, hash);
 			while (conn) {
 				if (conn->mux->takeover && conn->mux->takeover(conn, i, 0) == 0) {
-					conn_delete_from_tree(conn);
+					conn_delete_from_tree(conn, i);
 					_HA_ATOMIC_INC(&activity[tid].fd_takeover);
 					found = 1;
 					break;
@@ -1487,7 +1487,7 @@ takeover_random_idle_conn(struct eb_root *root, int curtid)
 		hash_node = eb64_entry(node, struct conn_hash_node, node);
 		conn = hash_node->conn;
 		if (conn && conn->mux->takeover && conn->mux->takeover(conn, curtid, 1) == 0) {
-			conn_delete_from_tree(conn);
+			conn_delete_from_tree(conn, curtid);
 			return conn;
 		}
 		node = eb64_next(node);
@@ -1744,7 +1744,7 @@ int be_reuse_connection(int64_t hash, struct session *sess,
 			if (avail <= 1) {
 				/* no more streams available, remove it from the list */
 				HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
-				conn_delete_from_tree(srv_conn);
+				conn_delete_from_tree(srv_conn, tid);
 				HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 			}
 
@@ -1852,7 +1852,7 @@ int connect_server(struct stream *s)
 		HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 		if (!LIST_ISEMPTY(&srv->per_thr[tid].idle_conn_list)) {
 			tokill_conn = LIST_ELEM(srv->per_thr[tid].idle_conn_list.n, struct connection *, idle_list);
-			conn_delete_from_tree(tokill_conn);
+			conn_delete_from_tree(tokill_conn, tid);
 			HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 
 			/* Release the idle lock before calling mux->destroy.
@@ -1881,7 +1881,7 @@ int connect_server(struct stream *s)
 
 				if (!LIST_ISEMPTY(&srv->per_thr[i].idle_conn_list)) {
 					tokill_conn = LIST_ELEM(srv->per_thr[i].idle_conn_list.n, struct connection *, idle_list);
-					conn_delete_from_tree(tokill_conn);
+					conn_delete_from_tree(tokill_conn, i);
 				}
 				HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[i].idle_conns_lock);
 
diff --git a/src/connection.c b/src/connection.c
index 39e2eb3c8..896dbc1a7 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -73,12 +73,13 @@ struct conn_tlv_list *conn_get_tlv(struct connection *conn, int type)
 	return NULL;
 }
 
-/* Remove <conn> idle connection from its attached tree (idle, safe or avail).
- * If also present in the secondary server idle list, conn is removed from it.
+/* Remove <conn> idle connection from its attached tree (idle, safe or avail)
+ * for the server in the connection's target and thread <thr>. If also present
+ * in the secondary server idle list, conn is removed from it.
  *
  * Must be called with idle_conns_lock held.
  */
-void conn_delete_from_tree(struct connection *conn)
+void conn_delete_from_tree(struct connection *conn, int thr)
 {
 	LIST_DEL_INIT(&conn->idle_list);
 	eb64_delete(&conn->hash_node->node);
@@ -209,7 +210,7 @@ int conn_notify_mux(struct connection *conn, int old_flags, int forced_wake)
 					conn_in_list = 0;
 			}
 			else {
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, tid);
 			}
 			HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 		}
diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index caac5450d..fc714d5a8 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -3068,7 +3068,7 @@ struct task *fcgi_io_cb(struct task *t, void *ctx, unsigned int state)
 					conn_in_list = 0;
 			}
 			else {
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, tid);
 			}
 		}
 
@@ -3329,7 +3329,7 @@ struct task *fcgi_timeout_task(struct task *t, void *context, unsigned int state
 		 * to steal it from us.
 		 */
 		if (fconn->conn->flags & CO_FL_LIST_MASK)
-			conn_delete_from_tree(fconn->conn);
+			conn_delete_from_tree(fconn->conn, tid);
 		else if (fconn->conn->flags & CO_FL_SESS_IDLE)
 			session_detach_idle_conn(fconn->conn->owner, fconn->conn);
 
diff --git a/src/mux_h1.c b/src/mux_h1.c
index d68582a97..234c26741 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -4311,7 +4311,7 @@ struct task *h1_io_cb(struct task *t, void *ctx, unsigned int state)
 					conn_in_list = 0;
 			}
 			else {
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, tid);
 			}
 		}
 
@@ -4451,7 +4451,7 @@ struct task *h1_timeout_task(struct task *t, void *context, unsigned int state)
 		 * to steal it from us.
 		 */
 		if (h1c->conn->flags & CO_FL_LIST_MASK)
-			conn_delete_from_tree(h1c->conn);
+			conn_delete_from_tree(h1c->conn, tid);
 
 		HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 
diff --git a/src/mux_h2.c b/src/mux_h2.c
index a64e432dc..309e06e63 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -4966,7 +4966,7 @@ struct task *h2_io_cb(struct task *t, void *ctx, unsigned int state)
 					conn_in_list = 0;
 			}
 			else {
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, tid);
 			}
 		}
 
@@ -5143,7 +5143,7 @@ static int h2_process(struct h2c *h2c)
 		/* connections in error must be removed from the idle lists */
 		if (conn->flags & CO_FL_LIST_MASK) {
 			HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
-			conn_delete_from_tree(conn);
+			conn_delete_from_tree(conn, tid);
 			HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 		}
 	}
@@ -5151,7 +5151,7 @@ static int h2_process(struct h2c *h2c)
 		/* connections in error must be removed from the idle lists */
 		if (conn->flags & CO_FL_LIST_MASK) {
 			HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
-			conn_delete_from_tree(conn);
+			conn_delete_from_tree(conn, tid);
 			HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 		}
 	}
@@ -5259,7 +5259,7 @@ struct task *h2_timeout_task(struct task *t, void *context, unsigned int state)
 		 * to steal it from us.
 		 */
 		if (h2c->conn->flags & CO_FL_LIST_MASK)
-			conn_delete_from_tree(h2c->conn);
+			conn_delete_from_tree(h2c->conn, tid);
 		else if (h2c->conn->flags & CO_FL_SESS_IDLE)
 			session_detach_idle_conn(h2c->conn->owner, h2c->conn);
 
@@ -5341,7 +5341,7 @@ do_leave:
 	/* in any case this connection must not be considered idle anymore */
 	if (h2c->conn->flags & CO_FL_LIST_MASK) {
 		HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
-		conn_delete_from_tree(h2c->conn);
+		conn_delete_from_tree(h2c->conn, tid);
 		HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 	}
 
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 1dd01534b..e51c99fb6 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -3205,7 +3205,7 @@ static void qcc_shutdown(struct qcc *qcc)
 
 	/* A connection is not reusable if app layer is closed. */
 	if (qcc->flags & QC_CF_IS_BACK)
-		conn_delete_from_tree(qcc->conn);
+		conn_delete_from_tree(qcc->conn, tid);
 
  out:
 	qcc->app_st = QCC_APP_ST_SHUT;
@@ -3408,7 +3408,7 @@ struct task *qcc_io_cb(struct task *t, void *ctx, unsigned int state)
 			if (conn->flags & CO_FL_SESS_IDLE)
 				session_detach_idle_conn(conn->owner, conn);
 			else
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, tid);
 		}
 
 		HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
@@ -3532,7 +3532,7 @@ static struct task *qcc_timeout_task(struct task *t, void *ctx, unsigned int sta
 		 * attempts to steal it from us.
 		 */
 		if (qcc->conn->flags & CO_FL_LIST_MASK)
-			conn_delete_from_tree(qcc->conn);
+			conn_delete_from_tree(qcc->conn, tid);
 		else if (qcc->conn->flags & CO_FL_SESS_IDLE)
 			session_unown_conn(qcc->conn->owner, qcc->conn);
 
diff --git a/src/mux_spop.c b/src/mux_spop.c
index b1cb2676c..2583b3c9e 100644
--- a/src/mux_spop.c
+++ b/src/mux_spop.c
@@ -2564,7 +2564,7 @@ static struct task *spop_io_cb(struct task *t, void *ctx, unsigned int state)
 					conn_in_list = 0;
 			}
 			else {
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, tid);
 			}
 		}
 
@@ -2676,7 +2676,7 @@ static int spop_process(struct spop_conn *spop_conn)
 		/* connections in error must be removed from the idle lists */
 		if (conn->flags & CO_FL_LIST_MASK) {
 			HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
-			conn_delete_from_tree(conn);
+			conn_delete_from_tree(conn, tid);
 			HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 		}
 	}
@@ -2799,7 +2799,7 @@ static struct task *spop_timeout_task(struct task *t, void *context, unsigned in
 		 * to steal it from us.
 		 */
 		if (spop_conn->conn->flags & CO_FL_LIST_MASK)
-			conn_delete_from_tree(spop_conn->conn);
+			conn_delete_from_tree(spop_conn->conn, tid);
 		else if (spop_conn->conn->flags & CO_FL_SESS_IDLE)
 			session_detach_idle_conn(spop_conn->conn->owner, spop_conn->conn);
 
diff --git a/src/server.c b/src/server.c
index 1f17e4a04..2ce1151be 100644
--- a/src/server.c
+++ b/src/server.c
@@ -7188,7 +7188,7 @@ static int srv_migrate_conns_to_remove(struct server *srv, int thr, int toremove
 			break;
 
 		conn = LIST_ELEM(srv->per_thr[thr].idle_conn_list.n, struct connection *, idle_list);
-		conn_delete_from_tree(conn);
+		conn_delete_from_tree(conn, thr);
 		MT_LIST_APPEND(&idle_conns[thr].toremove_conns, &conn->toremove_list);
 		i++;
 	}
@@ -7263,7 +7263,7 @@ void srv_release_conn(struct server *srv, struct connection *conn)
 	/* Remove the connection from any tree (safe, idle or available) */
 	if (conn->hash_node) {
 		HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
-		conn_delete_from_tree(conn);
+		conn_delete_from_tree(conn, tid);
 		conn->flags &= ~CO_FL_LIST_MASK;
 		HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 	}
@@ -7361,7 +7361,7 @@ int srv_add_to_idle_list(struct server *srv, struct connection *conn, int is_saf
 		_HA_ATOMIC_DEC(&srv->curr_used_conns);
 
 		HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
-		conn_delete_from_tree(conn);
+		conn_delete_from_tree(conn, tid);
 
 		if (is_safe) {
 			conn->flags = (conn->flags & ~CO_FL_LIST_MASK) | CO_FL_SAFE_LIST;
@@ -7523,7 +7523,7 @@ static void srv_close_idle_conns(struct server *srv)
 
 				if (conn->ctrl->ctrl_close)
 					conn->ctrl->ctrl_close(conn);
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, i);
 			}
 		}
 	}
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 5c320987f..e77d8eeef 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -6422,7 +6422,7 @@ struct task *ssl_sock_io_cb(struct task *t, void *context, unsigned int state)
 					conn_in_list = 0;
 			}
 			else {
-				conn_delete_from_tree(conn);
+				conn_delete_from_tree(conn, tid);
 			}
 		}