diff --git a/include/haproxy/server.h b/include/haproxy/server.h
index fdb285c..66dcaf9 100644
--- a/include/haproxy/server.h
+++ b/include/haproxy/server.h
@@ -299,6 +299,7 @@
 	/* Remove the connection from any tree (safe, idle or available) */
 	HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 	conn_delete_from_tree(&conn->hash_node->node);
+	conn->flags &= ~CO_FL_LIST_MASK;
 	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 7334b56..f84b0bf 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -3215,8 +3215,10 @@
 		/* We're about to destroy the connection, so make sure nobody attempts
 		 * to steal it from us.
 		 */
-		if (fconn->conn->flags & CO_FL_LIST_MASK)
+		if (fconn->conn->flags & CO_FL_LIST_MASK) {
 			conn_delete_from_tree(&fconn->conn->hash_node->node);
+			fconn->conn->flags &= ~CO_FL_LIST_MASK;
+		}
 
 		HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 	}
diff --git a/src/mux_h1.c b/src/mux_h1.c
index c29c4ed..e6a9392 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -3036,8 +3036,10 @@
 		/* We're about to destroy the connection, so make sure nobody attempts
 		 * to steal it from us.
 		 */
-		if (h1c->conn->flags & CO_FL_LIST_MASK)
+		if (h1c->conn->flags & CO_FL_LIST_MASK) {
 			conn_delete_from_tree(&h1c->conn->hash_node->node);
+			h1c->conn->flags &= ~CO_FL_LIST_MASK;
+		}
 
 		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 fb9e48a..17446f1 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -4096,6 +4096,7 @@
 		if (conn->flags & CO_FL_LIST_MASK) {
 			HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 			conn_delete_from_tree(&conn->hash_node->node);
+			conn->flags &= ~CO_FL_LIST_MASK;
 			HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 		}
 	}
@@ -4104,6 +4105,7 @@
 		if (conn->flags & CO_FL_LIST_MASK) {
 			HA_SPIN_LOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 			conn_delete_from_tree(&conn->hash_node->node);
+			conn->flags &= ~CO_FL_LIST_MASK;
 			HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 		}
 	}
@@ -4184,8 +4186,10 @@
 		/* We're about to destroy the connection, so make sure nobody attempts
 		 * to steal it from us.
 		 */
-		if (h2c->conn->flags & CO_FL_LIST_MASK)
+		if (h2c->conn->flags & CO_FL_LIST_MASK) {
 			conn_delete_from_tree(&h2c->conn->hash_node->node);
+			h2c->conn->flags &= ~CO_FL_LIST_MASK;
+		}
 
 		HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 	}
@@ -4238,6 +4242,7 @@
 	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->hash_node->node);
+		h2c->conn->flags &= ~CO_FL_LIST_MASK;
 		HA_SPIN_UNLOCK(IDLE_CONNS_LOCK, &idle_conns[tid].idle_conns_lock);
 	}
 
diff --git a/src/server.c b/src/server.c
index df67e1d..93481dc 100644
--- a/src/server.c
+++ b/src/server.c
@@ -5463,6 +5463,7 @@
 
 		hash_node = ebmb_entry(node, struct conn_hash_node, node);
 		eb_delete(node);
+		hash_node->conn->flags &= ~CO_FL_LIST_MASK;
 		MT_LIST_APPEND(toremove_list, &hash_node->conn->toremove_list);
 		i++;