1 files changed, 1 insertions, 0 deletions
diff --git a/sprintf.c b/sprintf.c
index b41ab9cb39..3642e2153a 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -1174,6 +1174,7 @@ ruby__sfvwrite(register rb_printf_buffer *fp, register struct __suio *uio)
 	len -= n;
     }
     fp->_p = (unsigned char *)buf;
+    rb_str_set_len(result, buf - RSTRING_PTR(result));
     return 0;
 }