diff --git a/artiq/coredevice/suservo.py b/artiq/coredevice/suservo.py
index f1ce004e5..2011bba2d 100644
--- a/artiq/coredevice/suservo.py
+++ b/artiq/coredevice/suservo.py
@@ -284,7 +284,7 @@ class Channel:
         """
         base = (self.servo_channel << 8) | (profile << 3)
         self.servo.write(base + 0, ftw >> 16)
-        self.servo.write(base + 6, ftw)
+        self.servo.write(base + 6, (ftw & 0xffff))
         self.servo.write(base + 4, offs)
         self.servo.write(base + 2, pow_)