1 files changed, 1 insertions, 0 deletions
diff --git a/vm.c b/vm.c
index ea138cc862..52e1f070bf 100644
--- a/vm.c
+++ b/vm.c
@@ -2357,6 +2357,7 @@ core_hash_merge_kwd(int argc, VALUE *argv)
     hash = argv[0];
     kw = argv[argc-1];
     kw = rb_convert_type(kw, T_HASH, "Hash", "to_hash");
+    if (argc < 2) hash = kw;
     rb_hash_foreach(kw, argc < 2 ? kwcheck_i : kwmerge_i, hash);
     return hash;
 }