diff --git a/core/config.class.inc.php b/core/config.class.inc.php
index 82d8a786e..970b7e3b7 100644
--- a/core/config.class.inc.php
+++ b/core/config.class.inc.php
@@ -2685,14 +2685,13 @@ class Config
 	 *
 	 * @param array $aParamValues
 	 * @param ?string $sModulesDir
-	 * @param bool $bPreserveModuleSettings
 	 *
 	 * @return void The current object is modified directly
 	 *
 	 * @throws \Exception
 	 * @throws \CoreException
 	 */
-	public function UpdateFromParams($aParamValues, $sModulesDir = null, $bPreserveModuleSettings = false)
+	public function UpdateFromParams($aParamValues, $sModulesDir = null)
 	{
 		if (isset($aParamValues['application_path'])) {
 			$this->Set('app_root_url', $aParamValues['application_path']);
@@ -2740,7 +2739,10 @@ class Config
 		} else {
 			$aSelectedModules = null;
 		}
-		$this->UpdateIncludes($sModulesDir, $aSelectedModules);
+
+		if (! is_null($sModulesDir)) {
+			$this->UpdateIncludes($sModulesDir, $aSelectedModules);
+		}
 
 		if (isset($aParamValues['source_dir'])) {
 			$this->Set('source_dir', $aParamValues['source_dir']);
@@ -2758,12 +2760,8 @@ class Config
 	 *
 	 * @throws Exception
 	 */
-	public function UpdateIncludes($sModulesDir, $aSelectedModules = null)
+	public function UpdateIncludes(string $sModulesDir, $aSelectedModules = null)
 	{
-		if ($sModulesDir === null) {
-			return;
-		}
-
 		// Initialize the arrays below with default values for the application...
 		$oEmptyConfig = new Config('dummy_file', false); // Do NOT load any config file, just set the default values
 		$aAddOns = $oEmptyConfig->GetAddOns();
diff --git a/setup/applicationinstaller.class.inc.php b/setup/applicationinstaller.class.inc.php
index bb9b9de62..583da2476 100644
--- a/setup/applicationinstaller.class.inc.php
+++ b/setup/applicationinstaller.class.inc.php
@@ -46,6 +46,8 @@ class ApplicationInstaller
 	protected $oParams;
 	protected static $bMetaModelStarted = false;
 
+	protected Config $oConfig;
+
 	/**
 	 * @param \Parameters $oParams
 	 *
@@ -57,9 +59,9 @@ class ApplicationInstaller
 		$this->oParams = $oParams;
 
 		$aParamValues = $oParams->GetParamForConfigArray();
-		$oConfig = new Config();
-		$oConfig->UpdateFromParams($aParamValues, null);
-		utils::SetConfig($oConfig);
+		$this->oConfig = new Config();
+		$this->oConfig->UpdateFromParams($aParamValues);
+		utils::SetConfig($this->oConfig);
 	}
 
 	/**
@@ -238,11 +240,8 @@ class ApplicationInstaller
 					// __DB__-%Y-%m-%d
 					$sDestination = $aPreinstall['backup']['destination'];
 					$sSourceConfigFile = $aPreinstall['backup']['configuration_file'];
-					$aDBParams = $this->oParams->GetParamForConfigArray();
-					$oTempConfig = new Config();
-					$oTempConfig->UpdateFromParams($aDBParams);
 					$sMySQLBinDir = $this->oParams->Get('mysql_bindir', null);
-					self::DoBackup($oTempConfig, $sDestination, $sSourceConfigFile, $sMySQLBinDir);
+					self::DoBackup($this->oConfig, $sDestination, $sSourceConfigFile, $sMySQLBinDir);
 
 					$aResult = [
 						'status' => self::OK,
@@ -565,15 +564,9 @@ class ApplicationInstaller
 			$sConfigFilePath = utils::GetConfigFilePath($sEnvironment);
 			if (is_file($sConfigFilePath)) {
 				$oConfig = new Config($sConfigFilePath);
-			} else {
-				$oConfig = null;
-			}
-
-			if (false === is_null($oConfig)) {
 				$oConfig->UpdateFromParams($aParamValues);
+				SetupUtils::EnterMaintenanceMode($oConfig);
 			}
-
-			SetupUtils::EnterMaintenanceMode($oConfig);
 		}
 
 		if (!is_dir($sTargetPath)) {
@@ -682,11 +675,6 @@ class ApplicationInstaller
 		$oConfig = new Config();
 		$oConfig->UpdateFromParams($aParamValues, $sModulesDir);
 
-		if ($bOldAddon) {
-			// Old version of the add-on for backward compatibility with pre-2.0 data models
-			$oConfig->SetAddons([]);
-		}
-
 		$oProductionEnv = new RunTimeEnvironment($sTargetEnvironment);
 		$oProductionEnv->InitDataModel($oConfig, true);  // load data model only
 
@@ -860,11 +848,6 @@ class ApplicationInstaller
 		$oConfig = new Config();
 		$oConfig->UpdateFromParams($aParamValues, $sModulesDir);
 
-		if ($bOldAddon) {
-			// Old version of the add-on for backward compatibility with pre-2.0 data models
-			$oConfig->SetAddons([]);
-		}
-
 		$oProductionEnv = new RunTimeEnvironment($sTargetEnvironment);
 		$oProductionEnv->InitDataModel($oConfig, true);  // load data model and connect to the database
 		$oContextTag = new ContextTag(ContextTag::TAG_SETUP);
@@ -922,11 +905,6 @@ class ApplicationInstaller
 		$oConfig = new Config();
 		$oConfig->UpdateFromParams($aParamValues, $sModulesDir);
 
-		if ($bOldAddon) {
-			// Old version of the add-on for backward compatibility with pre-2.0 data models
-			$oConfig->SetAddons([]);
-		}
-
 		$oProductionEnv = new RunTimeEnvironment($sTargetEnvironment);
 
 		//Load the MetaModel if needed (asynchronous mode)
@@ -980,12 +958,10 @@ class ApplicationInstaller
 		$aParamValues['selected_modules'] = implode(',', $aSelectedModuleCodes);
 		$sMode = $aParamValues['mode'];
 
-		$bPreserveModuleSettings = false;
 		if ($sMode == 'upgrade') {
 			try {
 				$oOldConfig = new Config($sPreviousConfigFile);
 				$oConfig = clone($oOldConfig);
-				$bPreserveModuleSettings = true;
 			} catch (Exception $e) {
 				// In case the previous configuration is corrupted... start with a blank new one
 				$oConfig = new Config();
@@ -999,11 +975,7 @@ class ApplicationInstaller
 
 		$oConfig->Set('access_mode', ACCESS_FULL);
 		// Final config update: add the modules
-		$oConfig->UpdateFromParams($aParamValues, $sModulesDir, $bPreserveModuleSettings);
-		if ($bOldAddon) {
-			// Old version of the add-on for backward compatibility with pre-2.0 data models
-			$oConfig->SetAddons([]);
-		}
+		$oConfig->UpdateFromParams($aParamValues, $sModulesDir);
 
 		// Record which modules are installed...
 		$oProductionEnv = new RunTimeEnvironment($sTargetEnvironment);
diff --git a/setup/setuputils.class.inc.php b/setup/setuputils.class.inc.php
index 95ae569eb..b46e67fb3 100644
--- a/setup/setuputils.class.inc.php
+++ b/setup/setuputils.class.inc.php
@@ -1570,7 +1570,7 @@ JS
 
 		$aParamValues = $oWizard->GetParamForConfigArray();
 		$aParamValues['source_dir'] = $sRelativeSourceDir;
-		$oConfig->UpdateFromParams($aParamValues, null);
+		$oConfig->UpdateFromParams($aParamValues);
 
 		return $oConfig;
 	}
@@ -1627,7 +1627,7 @@ JS
 
 		$aParamValues = $oWizard->GetParamForConfigArray();
 		$aParamValues['source_dir'] = '';
-		$oConfig->UpdateFromParams($aParamValues, null);
+		$oConfig->UpdateFromParams($aParamValues);
 
 		$oProductionEnv = new RunTimeEnvironment();
 		return $oProductionEnv->GetApplicationVersion($oConfig);