1 files changed, 2 insertions, 0 deletions
diff --git a/enumerator.c b/enumerator.c
index bd039d28bc..7143e37636 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -492,6 +492,8 @@ enumerator_with_index(int argc, VALUE *argv, VALUE obj)
 
     rb_scan_args(argc, argv, "01", &memo);
     RETURN_SIZED_ENUMERATOR(obj, argc, argv, enumerator_size);
+    if (NIL_P(memo))
+	memo = INT2NUM(0);
     return enumerator_block_call(obj, enumerator_with_index_i, (VALUE)&memo);
 }