diff --git a/back/methods/machine-worker/add.js b/back/methods/machine-worker/add.js
index 65eb5d2975..92d0df78e3 100644
--- a/back/methods/machine-worker/add.js
+++ b/back/methods/machine-worker/add.js
@@ -37,27 +37,16 @@ module.exports = Self => {
 
             if (!machine) throw new Error(`plate ${plate} does not exist`);
 
-            const twelveHoursAgo = Date.vnNew();
-            twelveHoursAgo.setHours(twelveHoursAgo.getHours() - 12);
-
-            const isRegistered = await models.MachineWorker.findOne({
-                where: {
-                    and: [
-                        {machineFk: machine.id},
-                        {workerFk: userId},
-                        {outTime: {gte: twelveHoursAgo}}
-                    ]
-                }
-            }, myOptions);
-
-            if (!isRegistered) await models.MachineWorker.create({machineFk: machine.id, workerFk: userId}, myOptions);
-            else {
                 await models.MachineWorker.updateAll(
-                    {or: [{workerFk: userId}, {machineFk: machine.id}]},
+                    {
+                        or: [{workerFk: userId}, {machineFk: machine.id}],
+                        and: [{outTime: null }]
+                    },
                     {outTime: Date.vnNew()},
                     myOptions
                 );
-            }
+            
+            await models.MachineWorker.create({machineFk: machine.id, workerFk: userId}, myOptions);
 
             if (tx) await tx.commit();
         } catch (e) {