Pymodbus error with read_input_register function

Question

I am using pymodbus to test my electronic board. By using the RTU version I don't have any kind of problems, but when I test the TCP part, pymodbus fail and I don't understand why! The version of python is 3.9, and pymodbus is 2.5.3.

My code is:

from pymodbus.client.sync import ModbusTcpClient as ModbusClient

SERVER_HOST = '192.168.1.123'
SERVER_PORT = 502

if __name__ == '__main__':

    c = ModbusClient(SERVER_HOST, port=SERVER_PORT, timeout=4)
    c.connect()

    if not c.is_socket_open():
         if not c.connect():
            print("unable to connect!")

    ver = c.read_input_registers(
                    address=0x05, 
                    count=1, 
                    unit=1)

    assert(not ver.isError())

The error is:

Traceback (most recent call last):
  File "/Users/warcomeb/Projects/AMMICROSYSTEMS/LOCCIONI_BatterySimulator_CFirmware/test/test_modbustcp_basic.py", line 138, in <module>
    ver = c.read_input_registers(
  File "/usr/local/lib/python3.9/site-packages/pymodbus/client/common.py", line 125, in read_input_registers
    return self.execute(request)
  File "/usr/local/lib/python3.9/site-packages/pymodbus/client/sync.py", line 109, in execute
    return self.transaction.execute(request)
  File "/usr/local/lib/python3.9/site-packages/pymodbus/transaction.py", line 174, in execute
    response, last_exception = self._transact(
  File "/usr/local/lib/python3.9/site-packages/pymodbus/transaction.py", line 271, in _transact
    packet = self.client.framer.buildPacket(packet)
  File "/usr/local/lib/python3.9/site-packages/pymodbus/framer/socket_framer.py", line 206, in buildPacket
    data = message.encode()
  File "/usr/local/lib/python3.9/site-packages/pymodbus/register_read_message.py", line 33, in encode
    return struct.pack('>HH', self.address, self.count)
struct.error: required argument is not an integer