diff --git a/devices/util/lts_cold_start.py b/devices/util/lts_cold_start.py
index 9105904261e35f3ecd96510734cc14217a504955..18b2bbb01fdff1508a65beec5333a4572369000f 100644
--- a/devices/util/lts_cold_start.py
+++ b/devices/util/lts_cold_start.py
@@ -193,7 +193,7 @@ def lts_cold_start():
     adc_locked = numpy.array(pcc.RCU_ADC_lock_R)
     for rcu, i2c_status in enumerate(pcc.RCU_I2C_STATUS_R):
         if i2c_status == 0:
-            pcc.RCU_mask_RW[rcu] = True
+            rcu_mask[rcu] = True
             logging.info("RCU #{} is available.".format(rcu))
             for adc, adc_is_locked in enumerate(adc_locked[rcu]):
                 if adc_is_locked < 1: