diff --git a/klippy/cartesian.py b/klippy/cartesian.py
index de6eb1df..362ba555 100644
--- a/klippy/cartesian.py
+++ b/klippy/cartesian.py
@@ -6,8 +6,6 @@
 import logging
 import stepper, homing, chelper
 
-StepList = (0, 1, 2)
-
 class CartKinematics:
     def __init__(self, toolhead, config):
         self.printer = config.get_printer()
@@ -111,14 +109,14 @@ class CartKinematics:
         self.need_motor_enable = True
     def _check_motor_enable(self, print_time, move):
         need_motor_enable = False
-        for i in StepList:
+        for i, rail in enumerate(self.rails):
             if move.axes_d[i]:
-                self.rails[i].motor_enable(print_time, 1)
-            need_motor_enable |= not self.rails[i].is_motor_enabled()
+                rail.motor_enable(print_time, 1)
+            need_motor_enable |= not rail.is_motor_enabled()
         self.need_motor_enable = need_motor_enable
     def _check_endstops(self, move):
         end_pos = move.end_pos
-        for i in StepList:
+        for i in (0, 1, 2):
             if (move.axes_d[i]
                 and (end_pos[i] < self.limits[i][0]
                      or end_pos[i] > self.limits[i][1])):
@@ -149,9 +147,9 @@ class CartKinematics:
             move.start_pos[0], move.start_pos[1], move.start_pos[2],
             move.axes_d[0], move.axes_d[1], move.axes_d[2],
             move.start_v, move.cruise_v, move.accel)
-        for i in StepList:
+        for i, rail in enumerate(self.rails):
             if move.axes_d[i]:
-                self.rails[i].step_itersolve(self.cmove)
+                rail.step_itersolve(self.cmove)
     # Dual carriage support
     def _activate_carriage(self, carriage):
         toolhead = self.printer.lookup_object('toolhead')