1 files changed, 10 insertions, 6 deletions
diff --git a/hash.c b/hash.c
index c36b865869..43db7951ee 100644
--- a/hash.c
+++ b/hash.c
@@ -1917,6 +1917,8 @@ rb_hash_transform_keys(VALUE hash)
     return result;
 }
 
+static VALUE rb_hash_flatten(int argc, VALUE *argv, VALUE hash);
+
 /*
  *  call-seq:
  *     hsh.transform_keys! {|key| block } -> hsh
@@ -1940,12 +1942,14 @@ rb_hash_transform_keys_bang(VALUE hash)
     RETURN_SIZED_ENUMERATOR(hash, 0, 0, hash_enum_size);
     rb_hash_modify_check(hash);
     if (RHASH(hash)->ntbl) {
-	long i;
-	VALUE keys = rb_hash_keys(hash);
-	for (i = 0; i < RARRAY_LEN(keys); ++i) {
-	    VALUE key = RARRAY_AREF(keys, i), new_key = rb_yield(key);
-	    rb_hash_aset(hash, new_key, rb_hash_delete(hash, key));
-	}
+        long i;
+        VALUE pairs = rb_hash_flatten(0, NULL, hash);
+        rb_hash_clear(hash);
+        for (i = 0; i < RARRAY_LEN(pairs); i += 2) {
+            VALUE key = RARRAY_AREF(pairs, i), new_key = rb_yield(key),
+                  val = RARRAY_AREF(pairs, i+1);
+            rb_hash_aset(hash, new_key, val);
+        }
     }
     return hash;
 }