diff --git a/core/dbobjectsearch.class.php b/core/dbobjectsearch.class.php
index 0f32ab3efb..d702c1d0bf 100644
--- a/core/dbobjectsearch.class.php
+++ b/core/dbobjectsearch.class.php
@@ -1928,9 +1928,8 @@ public function GetExpectedArguments(): array
 
 	/**
 	 * @inheritDoc
-	 * @return DBObjectSearch
 	 */
-	protected function ApplyDataFilters(): DBObjectSearch
+	protected function ApplyDataFilters(): DBSearch
 	{
 		if ($this->IsAllDataAllowed() || $this->IsDataFiltered()) {
 			return $this;
diff --git a/core/dbunionsearch.class.php b/core/dbunionsearch.class.php
index a9118974fb..8566655aba 100644
--- a/core/dbunionsearch.class.php
+++ b/core/dbunionsearch.class.php
@@ -676,9 +676,8 @@ public function GetExpectedArguments(): array
 
 	/**
 	 * @inheritDoc
-	 * @return DBUnionSearch
 	 */
-	protected function ApplyDataFilters(): DBUnionSearch
+	protected function ApplyDataFilters(): DBSearch
 	{
 		if ($this->IsAllDataAllowed() || $this->IsDataFiltered()) {
 			return $this;
diff --git a/tests/php-unit-tests/unitary-tests/core/DBSearch/DBSearchApplyDataFiltersTest.php b/tests/php-unit-tests/unitary-tests/core/DBSearch/DBSearchApplyDataFiltersTest.php
new file mode 100644
index 0000000000..b503023b90
--- /dev/null
+++ b/tests/php-unit-tests/unitary-tests/core/DBSearch/DBSearchApplyDataFiltersTest.php
@@ -0,0 +1,67 @@
+<?php
+
+/*
+ * @copyright   Copyright (C) 2010-2026 Combodo SAS
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+
+namespace Combodo\iTop\Test\UnitTest\Core;
+
+use Combodo\iTop\Test\UnitTest\ItopDataTestCase;
+use DBObjectSearch;
+use DBUnionSearch;
+use UserRights;
+
+class DBSearchApplyDataFiltersTest extends ItopDataTestCase
+{
+	public const CREATE_TEST_ORG = true;
+
+	protected string $sOriginalUserRightsSelectModuleClass = '';
+
+	/**
+	 * @throws \Exception
+	 */
+	protected function setUp(): void
+	{
+		parent::setUp();
+
+		// Backup original UserRights select module as it will changed in some tests
+		$this->sOriginalUserRightsSelectModuleClass = get_class(UserRights::GetModuleInstance());
+
+		$this->RequireOnceUnitTestFile('Fixtures/N9687_CustomGetSelectFilterClass.php');
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function tearDown(): void
+	{
+		// Restore original UserRights select module to not interfere with next tests
+		UserRights::SelectModule($this->sOriginalUserRightsSelectModuleClass);
+
+		parent::tearDown();
+	}
+
+	public function testApplyDataFiltersOnDBObjectSearchShouldAcceptGetSelectFilterClassReturningDBUnionSearch()
+	{
+		// Use custom select filter that returns a DBUnionSearch
+		$sPreviousSelectModuleClass = get_class(UserRights::GetModuleInstance());
+		UserRights::SelectModule('\\Combodo\\iTop\\Test\\UnitTest\\Core\\Fixtures\\N9687_CustomGetSelectFilterClass');
+
+		// Create a user and login, otherwise the select filter won't apply
+		self::CreateUser('test_dbsearch_applydatafilters', 3);
+		UserRights::Login('test_dbsearch_applydatafilters');
+
+		// Create a person
+		$oCreatedPerson = $this->CreatePerson(microtime());
+
+		// Try to retrieve it using the select filter
+		$oSearch = DBObjectSearch::FromOQL("SELECT Person WHERE id = {$oCreatedPerson->GetKey()}");
+		$oFilteredSearch = $this->InvokeNonPublicMethod(DBObjectSearch::class, 'ApplyDataFilters', $oSearch);
+
+		// Restore original select module to not interfere with next tests
+		UserRights::SelectModule($sPreviousSelectModuleClass);
+
+		$this->assertEquals(DBUnionSearch::class, get_class($oFilteredSearch), "DBObjectSearch::ApplyDataFilters() should be able to return a \DBUnionSearch");
+	}
+}
diff --git a/tests/php-unit-tests/unitary-tests/core/DBSearch/Fixtures/N9687_CustomGetSelectFilterClass.php b/tests/php-unit-tests/unitary-tests/core/DBSearch/Fixtures/N9687_CustomGetSelectFilterClass.php
new file mode 100644
index 0000000000..fc2a53054b
--- /dev/null
+++ b/tests/php-unit-tests/unitary-tests/core/DBSearch/Fixtures/N9687_CustomGetSelectFilterClass.php
@@ -0,0 +1,24 @@
+<?php
+
+/*
+ * @copyright   Copyright (C) 2010-2026 Combodo SAS
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+
+namespace Combodo\iTop\Test\UnitTest\Core\Fixtures;
+
+use DBObjectSearch;
+use DBUnionSearch;
+use UserRightsProfile;
+
+class N9687_CustomGetSelectFilterClass extends UserRightsProfile
+{
+	public function GetSelectFilter($oUser, $sClass, $aSettings = [])
+	{
+		// We just need the method to return an union search
+		return new DBUnionSearch([
+			DBObjectSearch::FromOQL("SELECT $sClass WHERE 1!=2"),
+			DBObjectSearch::FromOQL("SELECT $sClass WHERE 1=1"),
+		]);
+	}
+}