diff --git a/eZ/Publish/Core/Persistence/Legacy/Tests/Content/MapperTest.php b/eZ/Publish/Core/Persistence/Legacy/Tests/Content/MapperTest.php
index 4923c188e3..f70dc66c16 100644
--- a/eZ/Publish/Core/Persistence/Legacy/Tests/Content/MapperTest.php
+++ b/eZ/Publish/Core/Persistence/Legacy/Tests/Content/MapperTest.php
@@ -243,7 +243,7 @@ public function testExtractContentFromRowsWithRemovedFieldDefinitions(): void
         $contentType = $this->getContentTypeFromRows($rowsFixture);
         $contentType->fieldDefinitions = array_filter(
             $contentType->fieldDefinitions,
-            static function (Content\Type\FieldDefinition $fieldDefinition) {
+            static function (Content\Type\FieldDefinition $fieldDefinition): bool {
                 // ref. fixtures, ezauthor
                 return $fieldDefinition->id !== 185;
             }