diff --git a/egs/librispeech/ASR/prepare.sh b/egs/librispeech/ASR/prepare.sh
index fca2c6cc4..93d010ea8 100755
--- a/egs/librispeech/ASR/prepare.sh
+++ b/egs/librispeech/ASR/prepare.sh
@@ -244,7 +244,7 @@ if [ $stage -le 6 ] && [ $stop_stage -ge 6 ]; then
     fi
 
     if [ ! -f $lang_dir/HL.fst ]; then
-      ./local/prepare_lang_fst.py  --lang-dir $lang_dir
+      ./local/prepare_lang_fst.py  --lang-dir $lang_dir --ngram-G ./data/lm/G_3_gram.fst.txt
     fi
   done
 fi