diff --git a/requirements_dev.txt b/requirements_dev.txt
index f6413e5..47028cc 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -6,7 +6,7 @@ matplotlib==2.0.2
 opencv-contrib-python==3.3.0.9
 opencv-python==3.3.0.9
 pillow==4.2.1
-pymodbus==1.3.2
+pymodbus==3.6.8
 pyserial==3.4
 PyYAML==4.2b1