diff --git a/requirements-modbus.txt b/requirements-modbus.txt
index 40ec150..641992b 100644
--- a/requirements-modbus.txt
+++ b/requirements-modbus.txt
@@ -1,2 +1,2 @@
 minimalmodbus	>=2.1,	<3
-pymodbus	>=3.8,	<4
+pymodbus	==3.8.0