diff --git a/site_ansto/instrument/bilby/config/motors/motor_configuration.tcl b/site_ansto/instrument/bilby/config/motors/motor_configuration.tcl
index d867dd7e..cd11c265 100644
--- a/site_ansto/instrument/bilby/config/motors/motor_configuration.tcl
+++ b/site_ansto/instrument/bilby/config/motors/motor_configuration.tcl
@@ -521,12 +521,13 @@ sicslist setatt gs_L2_curtaind long_name L2_curtaind
 
 ## Lt0
 proc Lt0 {} {
-    set t0_id [SplitReply [master_chopper_id]]
-    switch $t0_id {
-      "1" { set retval 0.0}
-      "2" { set retval 1100.0}
-      "3" { set retval 3300.0}
-      "4" { set retval 7700.0}
+    set master_id [SplitReply [master_chopper_id]]
+    switch $master_id {
+      1 { set retval 0.0}
+      2 { set retval 1100.0}
+      3 { set retval 3300.0}
+      4 { set retval 7700.0}
+      default {set retval "ERROR: master_id = $master_id"}
     }
     return "[lindex [info level 0] 0] = $retval"
 }