diff --git a/Tools/autotest/arduplane.py b/Tools/autotest/arduplane.py
index 4f386413d3..2dc4a23918 100644
--- a/Tools/autotest/arduplane.py
+++ b/Tools/autotest/arduplane.py
@@ -2738,7 +2738,10 @@ class AutoTestPlane(AutoTest):
         attempt_fence_breached_disable(start_mode="FBWA", end_mode="FBWA", expected_mode="GUIDED", action=6)
         attempt_fence_breached_disable(start_mode="FBWA", end_mode="FBWA", expected_mode="GUIDED", action=7)
 
-    def run_auxfunc(self, function, level):
+    def run_auxfunc(self,
+                    function,
+                    level,
+                    want_result=mavutil.mavlink.MAV_RESULT_ACCEPTED):
         self.run_cmd(
             mavutil.mavlink.MAV_CMD_DO_AUX_FUNCTION,
             function,  # p1
@@ -2748,6 +2751,7 @@ class AutoTestPlane(AutoTest):
             0,  # p5
             0,  # p6
             0,  # p7
+            want_result=want_result
         )
 
     def fly_aux_function(self):
@@ -2758,6 +2762,20 @@ class AutoTestPlane(AutoTest):
         self.wait_statustext("RevThrottle: DISABLE", check_context=True)
         self.run_auxfunc(65, 2)  # 65 == GPS_DISABLE
 
+        self.start_subtest("Bad auxfunc")
+        self.run_auxfunc(
+            65231,
+            2,
+            want_result=mavutil.mavlink.MAV_RESULT_FAILED
+        )
+
+        self.start_subtest("Bad switchpos")
+        self.run_auxfunc(
+            62,
+            17,
+            want_result=mavutil.mavlink.MAV_RESULT_DENIED
+        )
+
     def tests(self):
         '''return list of all tests'''
         ret = super(AutoTestPlane, self).tests()