Make temporary lock string encoding free

As a temporary lock string is hidden, it can not have instance
variables, including non-inlined encoding index.

1 files changed, 1 insertions, 1 deletions

diff --git a/sprintf.c b/sprintf.c
index 64cfdee1a1..ff1800e088 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -257,7 +257,7 @@ rb_str_format(int argc, const VALUE *argv, VALUE fmt)
     blen = 0;
     bsiz = 120;
     result = rb_str_buf_new(bsiz);
-    rb_enc_copy(result, fmt);
+    rb_enc_associate(result, enc);
     buf = RSTRING_PTR(result);
     memset(buf, 0, bsiz);
     ENC_CODERANGE_SET(result, coderange);