diff --git a/core/log.class.inc.php b/core/log.class.inc.php
index 9c9fbc396..c41b4e31f 100644
--- a/core/log.class.inc.php
+++ b/core/log.class.inc.php
@@ -15,6 +15,7 @@
 //
 //   You should have received a copy of the GNU Affero General Public License
 //   along with iTop. If not, see <http://www.gnu.org/licenses/>
+use Combodo\iTop\Test\UnitTest\ItopTestCase;
 
 
 /**
@@ -1071,16 +1072,19 @@ class DeprecatedCallsLog extends LogAPI
 	 * @uses \set_error_handler() to catch deprecated notices
 	 *
 	 * @since 3.0.0 N°3002 logs deprecated notices in called code
+	 * @since 3.0.4 N°6274 do not set handler when in PHPUnit context (otherwise PHP notices won't be caught)
 	 */
-	public static function Enable($sTargetFile = null): void
-	{
+	public static function Enable($sTargetFile = null): void {
 		if (empty($sTargetFile)) {
 			$sTargetFile = APPROOT.'log/deprecated-calls.log';
 		}
 		parent::Enable($sTargetFile);
 
-		if (static::IsLogLevelEnabledSafe(self::LEVEL_WARNING, self::ENUM_CHANNEL_PHP_LIBMETHOD)) {
-			set_error_handler([static::class, 'DeprecatedNoticesErrorHandler']);
+		if (
+			(false === defined(ItopTestCase::ITOP_PHPUNIT_RUNNING_CONSTANT_NAME))
+			&& static::IsLogLevelEnabledSafe(self::LEVEL_WARNING, self::ENUM_CHANNEL_PHP_LIBMETHOD)
+		) {
+			set_error_handler([static::class, 'DeprecatedNoticesErrorHandler'], E_DEPRECATED | E_USER_DEPRECATED);
 		}
 	}
 
diff --git a/tests/php-unit-tests/ItopTestCase.php b/tests/php-unit-tests/ItopTestCase.php
index 633e8884f..5dec2a274 100644
--- a/tests/php-unit-tests/ItopTestCase.php
+++ b/tests/php-unit-tests/ItopTestCase.php
@@ -32,13 +32,20 @@ use SetupUtils;
 
 define('DEBUG_UNIT_TEST', true);
 
-class ItopTestCase extends TestCase
-{
-	const TEST_LOG_DIR = 'test';
+class ItopTestCase extends TestCase {
+	/**
+	 * @since 3.0.4 N°6274 Allow to test if PHPUnit is currently running. Starting with PHPUnit 9.5 we'll be able to replace it with $GLOBALS['phpunit_version']
+	 */
+	public const ITOP_PHPUNIT_RUNNING_CONSTANT_NAME = 'ITOP_PHPUNIT_RUNNING';
+
+	public const TEST_LOG_DIR = 'test';
+
+	protected function setUp(): void {
+		if (false === defined(static::ITOP_PHPUNIT_RUNNING_CONSTANT_NAME)) {
+			// setUp might be called multiple times, so protecting the define() call !
+			define(static::ITOP_PHPUNIT_RUNNING_CONSTANT_NAME, true);
+		}
 
-	/** @noinspection UsingInclusionOnceReturnValueInspection avoid errors for approot includes */
-	protected function setUp(): void
-	{
 		$sAppRootRelPath = 'approot.inc.php';
 		$sDepthSeparator = '../';
 		for ($iDepth = 0; $iDepth < 8; $iDepth++) {
diff --git a/tests/php-unit-tests/unitary-tests/core/Log/DeprecatedCallsLogTest.php b/tests/php-unit-tests/unitary-tests/core/Log/DeprecatedCallsLogTest.php
new file mode 100644
index 000000000..6d01ec173
--- /dev/null
+++ b/tests/php-unit-tests/unitary-tests/core/Log/DeprecatedCallsLogTest.php
@@ -0,0 +1,41 @@
+<?php
+/*
+ * @copyright   Copyright (C) 2010-2023 Combodo SARL
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+
+namespace Combodo\iTop\Test\UnitTest\Core\Log;
+
+
+use Combodo\iTop\Test\UnitTest\ItopTestCase;
+use DeprecatedCallsLog;
+
+class DeprecatedCallsLogTest extends ItopTestCase {
+	public function testPhpNoticeWithoutDeprecatedCallsLog(): void {
+		$this->expectNotice();
+
+		$aArray = [];
+		if ('toto' === $aArray['tutu']) {
+			//Do nothing, just raising a undefined offset warning
+		}
+	}
+
+	/**
+	 * The error handler set by DeprecatedCallsLog during startup was causing PHPUnit to miss PHP notices like "undefined offset"
+	 *
+	 * The error handler is now disabled when running PHPUnit
+	 *
+	 * @since 3.0.4 N°6274
+	 * @covers DeprecatedCallsLog::DeprecatedNoticesErrorHandler
+	 */
+	public function testPhpNoticeWithDeprecatedCallsLog(): void {
+		$this->RequireOnceItopFile('core/log.class.inc.php');
+		DeprecatedCallsLog::Enable(); // will set error handler
+		$this->expectNotice();
+
+		$aArray = [];
+		if ('toto' === $aArray['tutu']) {
+			//Do nothing, just raising a undefined offset warning
+		}
+	}
+}