diff --git a/klippy/cartesian.py b/klippy/cartesian.py
index b2bc1b43..67c68be5 100644
--- a/klippy/cartesian.py
+++ b/klippy/cartesian.py
@@ -15,6 +15,8 @@ class CartKinematics:
                          for n in steppers]
         self.stepper_pos = [0, 0, 0]
     def build_config(self):
+        for stepper in self.steppers[:2]:
+            stepper.set_max_jerk(0.005 * stepper.max_accel) # XXX
         for stepper in self.steppers:
             stepper.build_config()
     def set_position(self, newpos):
diff --git a/klippy/extruder.py b/klippy/extruder.py
index 67ee13ed..25655dc9 100644
--- a/klippy/extruder.py
+++ b/klippy/extruder.py
@@ -14,6 +14,7 @@ class PrinterExtruder:
         self.stepper_pos = 0
     def build_config(self):
         self.heater.build_config()
+        self.stepper.set_max_jerk(9999999.9)
         self.stepper.build_config()
     def get_max_speed(self):
         return self.stepper.max_velocity, self.stepper.max_accel
diff --git a/klippy/stepper.py b/klippy/stepper.py
index 5a05e910..7c8438fc 100644
--- a/klippy/stepper.py
+++ b/klippy/stepper.py
@@ -15,6 +15,7 @@ class PrinterStepper:
         self.inv_step_dist = 1. / self.step_dist
         self.max_velocity = config.getfloat('max_velocity')
         self.max_accel = config.getfloat('max_accel')
+        self.max_jerk = 0.
 
         self.homing_speed = config.getfloat('homing_speed', 5.0)
         self.homing_positive_dir = config.getboolean(
@@ -26,6 +27,8 @@ class PrinterStepper:
 
         self.clock_ticks = None
         self.need_motor_enable = True
+    def set_max_jerk(self, max_jerk):
+        self.max_jerk = max_jerk
     def build_config(self):
         self.clock_ticks = self.printer.mcu.get_mcu_freq()
         max_error = self.config.getfloat('max_error', 0.000050)
@@ -33,9 +36,10 @@ class PrinterStepper:
 
         step_pin = self.config.get('step_pin')
         dir_pin = self.config.get('dir_pin')
-        jc = 0.005 # XXX
+        jc = self.max_jerk / self.max_accel
         inv_max_step_accel = self.step_dist / self.max_accel
-        min_stop_interval = int((math.sqrt(inv_max_step_accel + jc**2) - jc)
+        min_stop_interval = int((math.sqrt(3.*inv_max_step_accel + jc**2)
+                                 - math.sqrt(inv_max_step_accel + jc**2))
                                 * self.clock_ticks) - max_error
         min_stop_interval = max(0, min_stop_interval)
         mcu = self.printer.mcu