diff --git a/src/pygcode/gcodes.py b/src/pygcode/gcodes.py
index a2e5f34..7427a48 100644
--- a/src/pygcode/gcodes.py
+++ b/src/pygcode/gcodes.py
@@ -522,7 +522,7 @@ class GCodeCancelCannedCycle(GCodeMotion):
     modal_group = None
     exec_order = 241
 
-    def _process(self, machine):
+    def WRONG_process(self, machine):
         machine.mode.motion = None
 
 
diff --git a/src/pygcode/machine.py b/src/pygcode/machine.py
index 46c2ad5..2f31493 100644
--- a/src/pygcode/machine.py
+++ b/src/pygcode/machine.py
@@ -1,6 +1,9 @@
 import re
 from copy import copy, deepcopy
 from collections import defaultdict
+import logging
+
+log = logging.getLogger(__name__)
 
 from .gcodes import (
     MODAL_GROUP_MAP, GCode,
@@ -407,6 +410,10 @@ class Machine(object):
             self.state.cur_coord_sys = coord_sys_mode.coord_system_id
 
         # TODO: convert coord systems between inches/mm, G20/G21 respectively
+        # NOTE : on at least a Haas -- this cannot be changed when running a
+        # program -- the G20 / G21 codes don't actually change units, but if
+        # a G20 / G21 appears in the code and the machine settings do not match
+        # an error will be thrown.
 
     def modal_gcode(self, modal_params):
         """