1 files changed, 18 insertions, 4 deletions
diff --git a/hash.c b/hash.c
index a114773259..4fc7b88668 100644
--- a/hash.c
+++ b/hash.c
@@ -1702,12 +1702,26 @@ keys_i(VALUE key, VALUE value, VALUE ary)
 VALUE
 rb_hash_keys(VALUE hash)
 {
-    VALUE ary;
+    VALUE keys;
+    int size = RHASH_SIZE(hash);
 
-    ary = rb_ary_new_capa(RHASH_SIZE(hash));
-    rb_hash_foreach(hash, keys_i, ary);
+    keys = rb_ary_new_capa(size);
+    if (size == 0) return keys;
 
-    return ary;
+    if (ST_DATA_COMPATIBLE_P(VALUE)) {
+	st_table *table = RHASH(hash)->ntbl;
+
+	if (OBJ_PROMOTED(keys)) rb_gc_writebarrier_remember_promoted(keys);
+	RARRAY_PTR_USE(keys, ptr, {
+	    size = st_keys(table, ptr, size);
+	});
+	rb_ary_set_len(keys, size);
+    }
+    else {
+	rb_hash_foreach(hash, keys_i, keys);
+    }
+
+    return keys;
 }
 
 static int