diff --git a/ohmpi/hardware_system.py b/ohmpi/hardware_system.py
index 18aa01f26de35a320bebaa082ef56be2f8da5630..694e1425a967366a6e44f47c346286f3fe9b9af6 100644
--- a/ohmpi/hardware_system.py
+++ b/ohmpi/hardware_system.py
@@ -416,7 +416,7 @@ class OhmPiHardware:
             vab = np.min([np.abs(tx_volt), vab_max])
             if strategy == 'constant':
                 vab_max = vab
-                tx_volt = vab * .9
+                vab = vab * .9
                 strategy = 'vmax'
             vab_max = np.abs(vab_max)
             vmn_min = np.abs(vmn_min)