diff --git a/klippy/toolhead.py b/klippy/toolhead.py
index afb1ef0f..93c87331 100644
--- a/klippy/toolhead.py
+++ b/klippy/toolhead.py
@@ -459,7 +459,7 @@ class ToolHead:
         ffi_main, ffi_lib = chelper.get_ffi()
         ffi_lib.trapq_set_position(self.trapq, self.print_time,
                                    newpos[0], newpos[1], newpos[2])
-        self.commanded_pos[:] = newpos
+        self.commanded_pos[:3] = newpos[:3]
         self.kin.set_position(newpos, homing_axes)
         self.printer.send_event("toolhead:set_position")
     def limit_next_junction_speed(self, speed):