diff --git a/site_ansto/instrument/bilby/config/chopper/chopper.tcl b/site_ansto/instrument/bilby/config/chopper/chopper.tcl
index 537140d3..87d02deb 100644
--- a/site_ansto/instrument/bilby/config/chopper/chopper.tcl
+++ b/site_ansto/instrument/bilby/config/chopper/chopper.tcl
@@ -44,8 +44,8 @@ if [dict exists $::config_dict disk_chopper name] {
 }
 ::utility::macro::getset float t0_chopper_freq [subst { {chopper $ch_name} }] {
   set cid [SplitReply [t0_chopper_id]]
-  set rpm [hval /instrument/$chopper/disk_$cid/aspeed]
-  return "t0_chopper_freq = [expr $rpm / 60.0]"
+  set freq [hval /instrument/$chopper/disk_$cid/frequency]
+  return "t0_chopper_freq = $freq"
 }
 sicslist setatt t0_chopper_freq klass NXdisk_chopper
 sicslist setatt t0_chopper_freq long_name t0_chopper_freq