ERP Error

Traceback (innermost last):
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/app.py", line 48, in application
    frappe.local.http_request = frappe.auth.HTTPRequest()
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/auth.py", line 49, in __init__
    frappe.local.login_manager = LoginManager()
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/auth.py", line 93, in __init__
    self.make_session(resume=True)
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/auth.py", line 132, in make_session
    full_name=self.full_name, user_type=self.user_type)
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/sessions.py", line 144, in __init__
    else:
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/sessions.py", line 192, in resume
    if data:
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/sessions.py", line 205, in get_session_record
    if not r:
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/sessions.py", line 218, in get_session_data
    if not data:
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/sessions.py", line 231, in get_session_data_from_cache
    expiry = self.get_expiry_in_seconds(session_data.get("session_expiry"))
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/utils/data.py", line 146, in now
    """return current time in hh:mm"""
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/utils/data.py", line 108, in now_datetime
    return convert_utc_to_user_timezone(datetime.datetime.utcnow())
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/utils/data.py", line 136, in convert_utc_to_user_timezone
    return now_datetime().strftime(DATETIME_FORMAT)
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/utils/data.py", line 130, in get_user_time_zone
    def now():
  File "/home/erpnext/frappe-bench/apps/frappe/frappe/utils/redis_wrapper.py", line 115, in hget
    value = super(redis.Redis, self).hget(self.make_key(name), key)
  File "/home/erpnext/frappe-bench/env/local/lib/python2.7/site-packages/redis/client.py", line 1768, in hget
    return self.execute_command('HGET', name, key)
  File "/home/erpnext/frappe-bench/env/local/lib/python2.7/site-packages/redis/client.py", line 529, in execute_command
    return self.parse_response(connection, command_name, **options)
  File "/home/erpnext/frappe-bench/env/local/lib/python2.7/site-packages/redis/client.py", line 541, in parse_response
    response = connection.read_response()
  File "/home/erpnext/frappe-bench/env/local/lib/python2.7/site-packages/redis/connection.py", line 550, in read_response
    raise response
 ResponseError: WRONGTYPE Operation against a key holding the wrong kind of value