diff --git a/src/shared/att.c b/src/shared/att.c
index de35aef..63cd19b 100644
--- a/src/shared/att.c
+++ b/src/shared/att.c
@@ -64,6 +64,8 @@ struct bt_att {
 	bool in_disconn;
 	bool need_disconn_cleanup;
 
+	bool in_req;			/* There's a pending incoming request */
+
 	uint8_t *buf;
 	uint16_t mtu;
 
@@ -460,6 +462,9 @@ static bool can_write_data(struct io *io, void *user_data)
 	case ATT_OP_TYPE_IND:
 		att->pending_ind = op;
 		break;
+	case ATT_OP_TYPE_RSP:
+		/* Set in_req to false to indicate that no request is pending */
+		att->in_req = false;
 	default:
 		destroy_att_send_op(op);
 		return true;
@@ -604,6 +609,46 @@ static void handle_notify(struct bt_att *att, uint8_t opcode, uint8_t *pdu,
 	bt_att_unref(att);
 }
 
+static void disconn_handler(void *data, void *user_data)
+{
+	struct att_disconn *disconn = data;
+
+	if (disconn->removed)
+		return;
+
+	if (disconn->callback)
+		disconn->callback(disconn->user_data);
+}
+
+static bool disconnect_cb(struct io *io, void *user_data)
+{
+	struct bt_att *att = user_data;
+
+	io_destroy(att->io);
+	att->io = NULL;
+
+	util_debug(att->debug_callback, att->debug_data,
+						"Physical link disconnected");
+
+	bt_att_ref(att);
+	att->in_disconn = true;
+	queue_foreach(att->disconn_list, disconn_handler, NULL);
+	att->in_disconn = false;
+
+	if (att->need_disconn_cleanup) {
+		queue_remove_all(att->disconn_list, match_disconn_removed, NULL,
+							destroy_att_disconn);
+		att->need_disconn_cleanup = false;
+	}
+
+	bt_att_cancel_all(att);
+	bt_att_unregister_all(att);
+
+	bt_att_unref(att);
+
+	return false;
+}
+
 static bool can_read_data(struct io *io, void *user_data)
 {
 	struct bt_att *att = user_data;
@@ -635,6 +680,23 @@ static bool can_read_data(struct io *io, void *user_data)
 		util_debug(att->debug_callback, att->debug_data,
 				"ATT opcode cannot be handled: 0x%02x", opcode);
 		break;
+	case ATT_OP_TYPE_REQ:
+		/*
+		 * If a request is currently pending, then the sequential
+		 * protocol was violated. Disconnect the bearer and notify the
+		 * upper-layer.
+		 */
+		if (att->in_req) {
+			util_debug(att->debug_callback, att->debug_data,
+					"Received request while another is "
+					"pending: 0x%02x", opcode);
+			disconnect_cb(att->io, att);
+			return false;
+		}
+
+		att->in_req = true;
+
+		/* Fall through to the next case */
 	default:
 		/* For all other opcodes notify the upper layer of the PDU and
 		 * let them act on it.
@@ -648,46 +710,6 @@ static bool can_read_data(struct io *io, void *user_data)
 	return true;
 }
 
-static void disconn_handler(void *data, void *user_data)
-{
-	struct att_disconn *disconn = data;
-
-	if (disconn->removed)
-		return;
-
-	if (disconn->callback)
-		disconn->callback(disconn->user_data);
-}
-
-static bool disconnect_cb(struct io *io, void *user_data)
-{
-	struct bt_att *att = user_data;
-
-	io_destroy(att->io);
-	att->io = NULL;
-
-	util_debug(att->debug_callback, att->debug_data,
-						"Physical link disconnected");
-
-	bt_att_ref(att);
-	att->in_disconn = true;
-	queue_foreach(att->disconn_list, disconn_handler, NULL);
-	att->in_disconn = false;
-
-	if (att->need_disconn_cleanup) {
-		queue_remove_all(att->disconn_list, match_disconn_removed, NULL,
-							destroy_att_disconn);
-		att->need_disconn_cleanup = false;
-	}
-
-	bt_att_cancel_all(att);
-	bt_att_unregister_all(att);
-
-	bt_att_unref(att);
-
-	return false;
-}
-
 struct bt_att *bt_att_new(int fd)
 {
 	struct bt_att *att;