diff --git a/egs/librispeech/ASR/prepare.sh b/egs/librispeech/ASR/prepare.sh
index 59bed8389..b1d207049 100755
--- a/egs/librispeech/ASR/prepare.sh
+++ b/egs/librispeech/ASR/prepare.sh
@@ -123,10 +123,12 @@ if [ $stage -le 3 ] && [ $stop_stage -ge 3 ]; then
     touch data/fbank/.librispeech.done
   fi
 
-  cat <(gunzip -c data/fbank/librispeech_cuts_train-clean-100.jsonl.gz) \
-    <(gunzip -c data/fbank/librispeech_cuts_train-clean-360.jsonl.gz) \
-    <(gunzip -c data/fbank/librispeech_cuts_train-other-500.jsonl.gz) | \
-    shuf | gzip -c > data/fbank/librispeech_cuts_train-all-shuf.jsonl.gz
+  if [ ! -f data/fbank/librispeech_cuts_train-all-shuf.jsonl.gz ]; then
+    cat <(gunzip -c data/fbank/librispeech_cuts_train-clean-100.jsonl.gz) \
+      <(gunzip -c data/fbank/librispeech_cuts_train-clean-360.jsonl.gz) \
+      <(gunzip -c data/fbank/librispeech_cuts_train-other-500.jsonl.gz) | \
+      shuf | gzip -c > data/fbank/librispeech_cuts_train-all-shuf.jsonl.gz
+  fi
 
   if [ ! -e data/fbank/.librispeech-validated.done ]; then
     log "Validating data/fbank for LibriSpeech"
@@ -244,7 +246,7 @@ if [ $stage -le 6 ] && [ $stop_stage -ge 6 ]; then
 fi
 
 if [ $stage -le 7 ] && [ $stop_stage -ge 7 ]; then
-  log "Stage 7: Prepare bigram P"
+  log "Stage 7: Prepare bigram token-level P for MMI training"
 
   for vocab_size in ${vocab_sizes[@]}; do
     lang_dir=data/lang_bpe_${vocab_size}