diff --git a/setup/runtimeenv.class.inc.php b/setup/runtimeenv.class.inc.php
index 7d405724a..2a14c82f0 100644
--- a/setup/runtimeenv.class.inc.php
+++ b/setup/runtimeenv.class.inc.php
@@ -142,7 +142,7 @@ class RunTimeEnvironment
 	 * @param Config $oConfig Defines the target environment (DB)
 	 * @param mixed $modulesPath Either a single string or an array of absolute paths
 	 * @param bool $bAbortOnMissingDependency ...
-	 * @param array $aModulesToLoad List of modules to search for, defaults to all if ommitted
+	 * @param array $aModulesToLoad List of modules to search for, defaults to all if omitted
 	 *
 	 * @return array Array with the following format:
 	 * array =>
diff --git a/setup/setuputils.class.inc.php b/setup/setuputils.class.inc.php
index 71c3cbac0..4a42909e2 100644
--- a/setup/setuputils.class.inc.php
+++ b/setup/setuputils.class.inc.php
@@ -1466,7 +1466,8 @@ EOF
 	 * @param $oWizard
 	 * @param bool $bAbortOnMissingDependency ...
 	 * @param array $aModulesToLoad List of modules to search for, defaults to all if ommitted
-	 * @return hash
+	 *
+	 * @return array
 	 * @throws Exception
 	 */
 	public static function AnalyzeInstallation($oWizard, $bAbortOnMissingDependency = false, $aModulesToLoad = null)
@@ -1557,6 +1558,59 @@ EOF
 		return $oProductionEnv->GetApplicationVersion($oConfig);
 	}
 
+	/**
+	 * @param array $aModules List of available module codes
+	 *
+	 * @return bool true if we are in a iTop product package (professional, essential, ...)
+	 * @since 2.7.0 N°2533
+	 */
+	public static function IsProductVersion($aModules)
+	{
+		return array_key_exists('itsm-designer-connector', $aModules);
+	}
+
+	/**
+	 * @param array $aModules Available modules with code as key and metadata array as values
+	 *    Same structure as the one returned by {@link \RunTimeEnvironment::AnalyzeInstallation}
+	 * @param string $sExtensionsDir In the setup, get value with the 'extensions_dir' parameter
+	 *
+	 * @return string Error message if has manually installed modules, empty string otherwise
+	 *
+	 * @since 2.7.0 N°2533
+	 */
+	public static function CheckManualInstallDirEmpty($aModules, $sExtensionsDir = 'extensions')
+	{
+		if (!static::IsProductVersion($aModules))
+		{
+			return '';
+		}
+
+		$sManualInstallModulesFullPath = APPROOT.$sExtensionsDir.DIRECTORY_SEPARATOR;
+		$aManualInstallModules = array_filter($aModules,
+			static function ($v, $k) use ($sManualInstallModulesFullPath) {
+				if (!isset($v['root_dir'])) // avoid index undefined for the _Root_ entry
+				{
+					return false;
+				}
+				// calling realpath to avoid problems with dir separator (almost everywhere we are adding '/' instead of DIRECTORY_SEPARATOR)
+				$return = utils::RealPath($v['root_dir'], $sManualInstallModulesFullPath);
+				if ($return === false)
+				{
+					return false;
+				}
+
+				return true;
+			},
+			ARRAY_FILTER_USE_BOTH);
+
+		if (empty($aManualInstallModules))
+		{
+			return '';
+		}
+
+		return "Some modules are present in the '$sExtensionsDir' directory, this is not allowed when using ".ITOP_APPLICATION;
+	}
+
 	/**
 	 * Checks if the content of a directory matches the given manifest
 	 * @param string $sBaseDir Path to the root directory of iTop
diff --git a/setup/wizardsteps.class.inc.php b/setup/wizardsteps.class.inc.php
index 49e9712ac..e06ec3e3d 100644
--- a/setup/wizardsteps.class.inc.php
+++ b/setup/wizardsteps.class.inc.php
@@ -1272,6 +1272,7 @@ class WizStepModulesChoice extends WizardStep
 		if ($sConfigPath !== null) // only called if the config file exists : we are updating a previous installation !
 		{
 			$oConfig = new Config($sConfigPath);
+			utils::SetConfig($oConfig);
 			$this->bChoicesFromDatabase = $this->oExtensionsMap->LoadChoicesFromDatabase($oConfig);
 		}
 	}
@@ -1339,9 +1340,14 @@ class WizStepModulesChoice extends WizardStep
 		$this->DisplayStep($oPage);
 	}
 
+	/**
+	 * @param \SetupPage $oPage
+	 *
+	 * @throws \Exception
+	 */
 	protected function DisplayStep($oPage)
 	{
-		// Sanity check (not stopper, to let developpers go further...)
+		// Sanity check (not stopper, to let developers go further...)
 		try
 		{
 			SetupUtils::AnalyzeInstallation($this->oWizard, true);
@@ -1357,6 +1363,15 @@ class WizStepModulesChoice extends WizardStep
 		$oPage->add_style("div.choice a { text-decoration:none; font-weight: bold; color: #1C94C4 }");
 		$oPage->add_style("div.description { margin-left: 2em; }");
 		$oPage->add_style(".choice-disabled { color: #999; }");
+
+		$aModules = SetupUtils::AnalyzeInstallation($this->oWizard);
+		$sManualInstallError = SetupUtils::CheckManualInstallDirEmpty($aModules,
+			$this->oWizard->GetParameter('extensions_dir', 'extensions'));
+		if ($sManualInstallError !== '')
+		{
+			$oPage->warning($sManualInstallError);
+		}
+
 		$oPage->add('<table class="module-selection-banner"><tr>');
 		$sBannerPath = isset($aStepInfo['banner']) ? $aStepInfo['banner'] : '';
 		if (!empty($sBannerPath))
@@ -1380,12 +1395,7 @@ class WizStepModulesChoice extends WizardStep
 		$oPage->add('</tr></table>');
 
 		// Build the default choices
-		$aDefaults = array();
-		$aModules = SetupUtils::AnalyzeInstallation($this->oWizard);
 		$aDefaults = $this->GetDefaults($aStepInfo, $aModules);
-		//echo "<pre>aStepInfo:\n ".print_r($aStepInfo, true)."</pre>";
-		//echo "<pre>aDefaults:\n ".print_r($aDefaults, true)."</pre>";
-
 		$index = $this->GetStepIndex();
 
 		// retrieve the saved selection