diff --git a/requirements.txt b/requirements.txt
index 27729bd..de84472 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,7 @@
 PyYAML>=6.0 
 requests>=2.26.0 
 paho-mqtt>=1.5.1
-pymodbus>=2.5.3
+pymodbus==2.5.3
 SungrowModbusTcpClient>=0.1.5
 SungrowModbusWebClient>=0.3.2
 influxdb-client>=1.24.0