diff --git a/pybitflyer/async.py b/pybitflyer/async.py
index 8c8fc5e..c6cfd4e 100644
--- a/pybitflyer/async.py
+++ b/pybitflyer/async.py
@@ -50,12 +50,16 @@ async def request(self, endpoint, method="GET", params=None):
             try:
                 if method == 'GET':
                     async with s.get(url, params=params, timeout=self.timeout, headers=header) as r:
-                        contents_json = await r.json()
-                        return contents_json
+                        contents = await r.text()
+                        if len(contents) > 0:
+                            contents = json.loads(contents)
+                        return contents
                 else:  # method == "POST":
                     async with s.post(url, data=json.dumps(params), timeout=self.timeout, headers=header) as r:
-                        contents_json = await r.json()
-                        return contents_json
+                        contents = await r.text()
+                        if len(contents) > 0:
+                            contents = json.loads(contents)
+                        return contents
             except Exception as e:
                 print(e)
                 raise e