1 files changed, 1 insertions, 1 deletions
diff --git a/array.c b/array.c
index c271f5ed8c..18bceeb7c3 100644
--- a/array.c
+++ b/array.c
@@ -2765,7 +2765,7 @@ flatten(VALUE ary, int level, int *modified)
     st_data_t id;
 
     stack = rb_ary_new();
-    result = rb_ary_new();
+    result = ary_new(rb_class_of(ary), RARRAY_LEN(ary));
     memo = st_init_numtable();
     st_insert(memo, (st_data_t)ary, (st_data_t)Qtrue);
     *modified = 0;