diff --git a/.github/workflows/style_check.yml b/.github/workflows/style_check.yml
index 20c3363b4..2a743705a 100644
--- a/.github/workflows/style_check.yml
+++ b/.github/workflows/style_check.yml
@@ -45,7 +45,7 @@ jobs:
 
       - name: Install Python dependencies
         run: |
-          python3 -m pip install --upgrade pip black flake8
+          python3 -m pip install --upgrade pip black==21.6b0 flake8==3.9.2
 
       - name: Run flake8
         shell: bash
diff --git a/egs/librispeech/ASR/conformer_mmi_phone/pretrained.py b/egs/librispeech/ASR/conformer_mmi_phone/pretrained.py
index c63616d28..21fc17277 100755
--- a/egs/librispeech/ASR/conformer_mmi_phone/pretrained.py
+++ b/egs/librispeech/ASR/conformer_mmi_phone/pretrained.py
@@ -268,7 +268,7 @@ def main():
     )
     waves = [w.to(device) for w in waves]
 
-    logging.info(f"Decoding started")
+    logging.info("Decoding started")
     features = fbank(waves)
 
     features = pad_sequence(
@@ -338,7 +338,7 @@ def main():
         s += f"{filename}:\n{words}\n\n"
     logging.info(s)
 
-    logging.info(f"Decoding Done")
+    logging.info("Decoding Done")
 
 
 if __name__ == "__main__":