diff --git a/gentle/language_model.py b/gentle/language_model.py
index 46c596cb..14bc2dc2 100644
--- a/gentle/language_model.py
+++ b/gentle/language_model.py
@@ -112,12 +112,11 @@ def make_bigram_language_model(kaldi_seq, proto_langdir, **kwargs):
 
     hclg_filename = tempfile.mktemp(suffix='_HCLG.fst')
     try:
-        devnull = open(os.devnull, 'wb')
         subprocess.check_output([MKGRAPH_PATH,
                         proto_langdir,
                         txt_fst_file.name,
                         hclg_filename],
-                        stderr=devnull)
+                        stderr=subprocess.DEVNULL)
     except Exception as e:
         try:
             os.unlink(hclg_filename)