diff --git a/pytchat/__init__.py b/pytchat/__init__.py
index 05f72f2..d355558 100644
--- a/pytchat/__init__.py
+++ b/pytchat/__init__.py
@@ -2,7 +2,7 @@
 pytchat is a lightweight python library to browse youtube livechat without Selenium or BeautifulSoup.
 """
 __copyright__    = 'Copyright (C) 2019 taizan-hokuto'
-__version__      = '0.2.2'
+__version__      = '0.2.3'
 __license__      = 'MIT'
 __author__       = 'taizan-hokuto'
 __author_email__ = '55448286+taizan-hokuto@users.noreply.github.com'
diff --git a/pytchat/cli/__init__.py b/pytchat/cli/__init__.py
index 213f8e7..3dd4bc7 100644
--- a/pytchat/cli/__init__.py
+++ b/pytchat/cli/__init__.py
@@ -57,8 +57,8 @@ def main():
             else:
                 raise FileNotFoundError
             err = None
-            for _ in range(3): # retry 3 times
-                try:                
+            for _ in range(3):  # retry 3 times
+                try:
                     info = VideoInfo(video_id)
                     break
                 except (PatternUnmatchError, JSONDecodeError, InvalidVideoIdException) as e:
@@ -81,7 +81,7 @@ def main():
             print(f" output path: {path.resolve()}")
             duration = info.get_duration()
             pbar = ProgressBar(total=(duration * 1000), status="Extracting")
-            ex = Extractor(video_id,               
+            ex = Extractor(video_id,
                     callback=pbar._disp,
                     div=10)
             signal.signal(signal.SIGINT, (lambda a, b: cancel(ex, pbar)))
diff --git a/pytchat/exceptions.py b/pytchat/exceptions.py
index 9e498d1..1bd918c 100644
--- a/pytchat/exceptions.py
+++ b/pytchat/exceptions.py
@@ -43,7 +43,6 @@ class InvalidVideoIdException(Exception):
         self.doc = doc
 
 
-
 class UnknownConnectionError(Exception):
     pass
 
diff --git a/pytchat/tool/extract/asyncdl.py b/pytchat/tool/extract/asyncdl.py
index 55ee1dd..c04b687 100644
--- a/pytchat/tool/extract/asyncdl.py
+++ b/pytchat/tool/extract/asyncdl.py
@@ -16,6 +16,9 @@ REPLAY_URL = "https://www.youtube.com/live_chat_replay/" \
              "get_live_chat_replay?continuation="
 MAX_RETRY_COUNT = 3
 
+# Set to avoid duplicate parameters
+param_set = set()
+
 
 def _split(start, end, count, min_interval_sec=120):
     """
@@ -64,6 +67,10 @@ def ready_blocks(video_id, duration, div, callback):
         url = f"{REPLAY_URL}{quote(continuation)}&pbj=1"
         for _ in range(MAX_RETRY_COUNT):
             try:
+                if continuation in param_set:
+                    next_continuation, actions = None, []
+                    break
+                param_set.add(continuation)
                 resp = await session.get(url, headers=headers)
                 next_continuation, actions = parser.parse(resp.json())
                 break
@@ -112,6 +119,10 @@ def fetch_patch(callback, blocks, video_id):
         url = f"{REPLAY_URL}{quote(continuation)}&pbj=1"
         for _ in range(MAX_RETRY_COUNT):
             try:
+                if continuation in param_set:
+                    continuation, actions = None, []
+                    break
+                param_set.add(continuation)
                 resp = await session.get(url, headers=config.headers)
                 continuation, actions = parser.parse(resp.json())
                 break
diff --git a/pytchat/tool/extract/worker.py b/pytchat/tool/extract/worker.py
index f48fc03..261de10 100644
--- a/pytchat/tool/extract/worker.py
+++ b/pytchat/tool/extract/worker.py
@@ -7,7 +7,6 @@ from typing import Tuple
 class ExtractWorker:
     """
     ExtractWorker associates a download session with a block.
-
     When the worker finishes fetching, the block
     being fetched is splitted and assigned the free worker.