diff --git a/core/mutex.class.inc.php b/core/mutex.class.inc.php
index ea459d0bf..c0d8521f7 100644
--- a/core/mutex.class.inc.php
+++ b/core/mutex.class.inc.php
@@ -1,5 +1,5 @@
 <?php
-// Copyright (C) 2013 Combodo SARL
+// Copyright (C) 2013-2016 Combodo SARL
 //
 //   This file is part of iTop.
 //
@@ -24,7 +24,7 @@
  * Relies on MySQL locks because the API sem_get is not always present in the
  * installed PHP.    
  *
- * @copyright   Copyright (C) 2013 Combodo SARL
+ * @copyright   Copyright (C) 2013-2016 Combodo SARL
  * @license     http://opensource.org/licenses/AGPL-3.0
  */
 class iTopMutex
@@ -139,6 +139,36 @@ class iTopMutex
 		}
 		return ($res !== '0');
 	}
+	
+	/**
+	 *	Check if the mutex is locked WITHOUT TRYING TO ACQUIRE IT
+	 *	@returns bool True if the mutex is in use, false otherwise
+	 */
+	public function IsLocked()
+	{
+		if ($this->bLocked)
+		{
+			return true; // Already acquired
+		}
+		if (self::$aAcquiredLocks[$this->sName] > 0)
+		{
+			return true;
+		}
+	
+		$res = $this->QueryToScalar("SELECT IS_FREE_LOCK('".$this->sName."')"); // IS_FREE_LOCK detects some error cases that IS_USED_LOCK do not detect
+		if (is_null($res))
+		{
+			$sMsg = "MySQL Error, IS_FREE_LOCK('".$this->sName."') returned null. Error (".mysqli_errno($this->hDBLink).") = '".mysqli_error($this->hDBLink)."'";
+			IssueLog::Error($sMsg);
+			throw new Exception($sMsg);
+		}
+		else if ($res == '1')
+		{
+			// Lock is free
+			return false;
+		}
+		return true;
+	}
 
 	/**
 	 *	Release the mutex
diff --git a/datamodels/2.x/itop-backup/ajax.backup.php b/datamodels/2.x/itop-backup/ajax.backup.php
index 9e331c9ed..d6049a480 100644
--- a/datamodels/2.x/itop-backup/ajax.backup.php
+++ b/datamodels/2.x/itop-backup/ajax.backup.php
@@ -1,5 +1,5 @@
 <?php
-// Copyright (C) 2013-2015 Combodo SARL
+// Copyright (C) 2013-2016 Combodo SARL
 //
 //   This file is part of iTop.
 //
@@ -19,7 +19,7 @@
 /**
  * Backup from an interactive session
  *
- * @copyright   Copyright (C) 2013-215 Combodo SARL
+ * @copyright   Copyright (C) 2013-2016 Combodo SARL
  * @license     http://opensource.org/licenses/AGPL-3.0
  */
 
@@ -77,9 +77,8 @@ try
 
 		$sEnvironment = utils::ReadParam('environment', 'production', false, 'raw_data');
 		$oRestoreMutex = new iTopMutex('restore.'.$sEnvironment);
-		if ($oRestoreMutex->TryLock())
+		if (!$oRestoreMutex->IsLocked())
 		{
-			$oRestoreMutex->Unlock();
 			$sFile = utils::ReadParam('file', '', false, 'raw_data');
 			$sToken = str_replace(' ', '', (string)microtime());
 			$sTokenFile = APPROOT.'/data/restore.'.$sToken.'.tok';
diff --git a/datamodels/2.x/itop-backup/main.itop-backup.php b/datamodels/2.x/itop-backup/main.itop-backup.php
index d2cc37afa..e1803d5ba 100644
--- a/datamodels/2.x/itop-backup/main.itop-backup.php
+++ b/datamodels/2.x/itop-backup/main.itop-backup.php
@@ -1,5 +1,5 @@
 <?php
-// Copyright (C) 2014-2015 Combodo SARL
+// Copyright (C) 2014-2016 Combodo SARL
 //
 //   This program is free software; you can redistribute it and/or modify
 //   it under the terms of the GNU General Public License as published by
@@ -28,24 +28,8 @@ class BackupHandler extends ModuleHandlerAPI
 	{
 		try
 		{
-			$oBackupMutex = new iTopMutex('backup.'.utils::GetCurrentEnvironment());
-			if ($oBackupMutex->TryLock())
-			{
-				$oBackupMutex->Unlock();
-			}
-			else
-			{
-				// Not needed: the DB dump is done in a single transaction
-				//MetaModel::GetConfig()->Set('access_mode', ACCESS_READONLY, 'itop-backup');
-				//MetaModel::GetConfig()->Set('access_message', ' - '.dict::S('bkp-backup-running'), 'itop-backup');
-			}
-	
 			$oRestoreMutex = new iTopMutex('restore.'.utils::GetCurrentEnvironment());
-			if ($oRestoreMutex->TryLock())
-			{
-				$oRestoreMutex->Unlock();
-			}
-			else
+			if ($oRestoreMutex->IsLocked())
 			{
 				IssueLog::Info(__class__.'::'.__function__.' A user is trying to use iTop while a restore is running. The requested page is in read-only mode.');
 				MetaModel::GetConfig()->Set('access_mode', ACCESS_READONLY, 'itop-backup');
diff --git a/datamodels/2.x/itop-backup/status.php b/datamodels/2.x/itop-backup/status.php
index bcb3e7883..5666aa169 100644
--- a/datamodels/2.x/itop-backup/status.php
+++ b/datamodels/2.x/itop-backup/status.php
@@ -1,5 +1,5 @@
 <?php
-// Copyright (C) 2014 Combodo SARL
+// Copyright (C) 2016 Combodo SARL
 //
 //   This file is part of iTop.
 //
@@ -20,7 +20,7 @@
 /**
  * Monitor the backup
  *
- * @copyright   Copyright (C) 2013 Combodo SARL
+ * @copyright   Copyright (C) 2016 Combodo SARL
  * @license     http://opensource.org/licenses/AGPL-3.0
  */
 
@@ -169,14 +169,13 @@ try
 	}
 
 	$oRestoreMutex = new iTopMutex('restore.'.utils::GetCurrentEnvironment());
-	if ($oRestoreMutex->TryLock())
+	if ($oRestoreMutex->IsLocked())
 	{
-		$oRestoreMutex->Unlock();
-		$sDisableRestore = '';
+		$sDisableRestore = 'disabled="disabled"';
 	}
 	else
 	{
-		$sDisableRestore = 'disabled="disabled"';
+		$sDisableRestore = '';
 	}
 	
 	// 1st table: list the backups made in the background
@@ -271,20 +270,12 @@ try
 	// Ongoing operation ?
 	//
 	$oBackupMutex = new iTopMutex('backup.'.utils::GetCurrentEnvironment());
-	if ($oBackupMutex->TryLock())
-	{
-		$oBackupMutex->Unlock();
-	}
-	else
+	if ($oBackupMutex->IsLocked())
 	{
 		$oP->p(Dict::S('bkp-backup-running'));
 	}
 	$oRestoreMutex = new iTopMutex('restore.'.utils::GetCurrentEnvironment());
-	if ($oRestoreMutex->TryLock())
-	{
-		$oRestoreMutex->Unlock();
-	}
-	else
+	if ($oRestoreMutex->IsLocked())
 	{
 		$oP->p(Dict::S('bkp-restore-running'));
 	}
diff --git a/setup/wizardsteps.class.inc.php b/setup/wizardsteps.class.inc.php
index 268f5afb3..072f860b7 100644
--- a/setup/wizardsteps.class.inc.php
+++ b/setup/wizardsteps.class.inc.php
@@ -1,5 +1,5 @@
 <?php
-// Copyright (C) 2010-2012 Combodo SARL
+// Copyright (C) 2010-2016 Combodo SARL
 //
 //   This file is part of iTop.
 //
@@ -18,7 +18,7 @@
 
 /**
  * All the steps of the iTop installation wizard
- * @copyright   Copyright (C) 2010-2012 Combodo SARL
+ * @copyright   Copyright (C) 2010-2016 Combodo SARL
  * @license     http://opensource.org/licenses/AGPL-3.0
  */
 
@@ -624,11 +624,7 @@ EOF
 				$this->oWizard->GetParameter('db_user', ''),
 				$this->oWizard->GetParameter('db_pwd', '')
 			);
-			if ($oMutex->TryLock())
-			{
-				$oMutex->Unlock();
-			}
-			else
+			if ($oMutex->IsLocked())
 			{
 				$oPage->p("<img src=\"../images/error.png\"/>&nbsp;An iTop CRON process is being executed on the target database. It is highly recommended to stop any iTop CRON process prior to running the setup program.");
 			}