diff --git a/src/ActiveQuery.php b/src/ActiveQuery.php
index 6d93bddf5..d583855ea 100644
--- a/src/ActiveQuery.php
+++ b/src/ActiveQuery.php
@@ -329,9 +329,9 @@ private function removeDuplicatedModels(array $models): array
             }
 
             if (count($pks) === 1) {
-                $hash = array_map(static fn ($model) => $model->getPrimaryKey(), $models);
+                $hash = array_map(static fn ($model): mixed => $model->getPrimaryKey(), $models);
             } else {
-                $hash = array_map(static fn ($model) => serialize($model->getPrimaryKey(true)), $models);
+                $hash = array_map(static fn ($model): mixed => serialize($model->getPrimaryKey(true)), $models);
             }
         }