diff --git a/TimeBaseAOMDriver/labscript_devices.py b/TimeBaseAOMDriver/labscript_devices.py
index 231ed6b7614cec4746c67946d47ff32d1cb09755..352f12e0dfaf3904d7e336fd57bc3e9e72f90a83 100644
--- a/TimeBaseAOMDriver/labscript_devices.py
+++ b/TimeBaseAOMDriver/labscript_devices.py
@@ -102,7 +102,7 @@ class TimeBaseAOM(Device):
         if step_time < 0 or step_time > 65535:
             raise LabscriptError(f"Start frequency of segment must be within [3.90625,255.996]ns!")
 
-        self.segments.append(f"1;{round(start_freq)};{round(stop_freq)};{round(step_freq)};{step_time};0")
+        self.segments.append(f";1;{round(start_freq)};{round(stop_freq)};{round(step_freq)};{step_time};0")
 
 
 class TimeBaseFreqSweepTrigger(DigitalOut):