diff --git a/Tools/ardupilotwaf/chibios.py b/Tools/ardupilotwaf/chibios.py
index c92acde02b..c0fb8e43bb 100644
--- a/Tools/ardupilotwaf/chibios.py
+++ b/Tools/ardupilotwaf/chibios.py
@@ -13,6 +13,8 @@ import shutil
 import sys
 import re
 import pickle
+import zlib
+import struct
 
 _dynamic_env_data = {}
 def _load_dynamic_env_data(bld):
@@ -93,6 +95,46 @@ class generate_bin(Task.Task):
     def __str__(self):
         return self.outputs[0].path_from(self.generator.bld.bldnode)
 
+def to_unsigned(i):
+    '''convert a possibly signed integer to unsigned'''
+    if i < 0:
+        i += 2**32
+    return i
+
+class set_app_descriptor(Task.Task):
+    '''setup app descriptor in bin file'''
+    color='BLUE'
+    always_run = True
+    def keyword(self):
+        return "app_descriptor"
+    def run(self):
+        if not 'APP_DESCRIPTOR' in self.env:
+            return
+        if self.env.APP_DESCRIPTOR == 'MissionPlanner':
+            descriptor = b'\x40\xa2\xe4\xf1\x64\x68\x91\x06'
+        else:
+            Logs.error("Bad APP_DESCRIPTOR %s" % self.env.APP_DESCRIPTOR)
+            return
+        img = open(self.inputs[0].abspath(), 'rb').read()
+        offset = img.find(descriptor)
+        if offset == -1:
+            Logs.error("Failed to find %s APP_DESCRIPTOR" % self.env.APP_DESCRIPTOR)
+            return
+        offset += 8
+        # next 8 bytes is 64 bit CRC. We set first 4 bytes to
+        # CRC32 of image before descriptor and 2nd 4 bytes
+        # to CRC32 of image after descriptor. This is very efficient
+        # for bootloader to calculate
+        # after CRC comes image length and 32 bit git hash
+        desc_len = 16
+        crc1 = to_unsigned(zlib.crc32(img[:offset]))
+        crc2 = to_unsigned(zlib.crc32(img[offset+desc_len:]))
+        githash = to_unsigned(int('0x' + self.generator.bld.git_head_hash(short=True),16))
+        desc = struct.pack('<IIII', crc1, crc2, len(img), githash)
+        img = img[:offset] + desc + img[offset+desc_len:]
+        Logs.info("Applying %s APP_DESCRIPTOR %08x%08x" % (self.env.APP_DESCRIPTOR, crc1, crc2))
+        open(self.inputs[0].abspath(), 'wb').write(img)
+
 class generate_apj(Task.Task):
     '''generate an apj firmware file'''
     color='CYAN'
@@ -148,6 +190,7 @@ def chibios_firmware(self):
     self.link_task.always_run = True
 
     link_output = self.link_task.outputs[0]
+    hex_task = None
 
     bin_target = self.bld.bldnode.find_or_declare('bin/' + link_output.change_ext('.bin').name)
     apj_target = self.bld.bldnode.find_or_declare('bin/' + link_output.change_ext('.apj').name)
@@ -177,7 +220,14 @@ def chibios_firmware(self):
                                                src=link_output)
         default_params_task.set_run_after(self.link_task)
         generate_bin_task.set_run_after(default_params_task)
-    
+
+    if self.env.APP_DESCRIPTOR:
+        app_descriptor_task = self.create_task('set_app_descriptor', src=bin_target)
+        app_descriptor_task.set_run_after(generate_bin_task)
+        generate_apj_task.set_run_after(app_descriptor_task)
+        if hex_task is not None:
+            hex_task.set_run_after(app_descriptor_task)
+
     if self.bld.options.upload:
         _upload_task = self.create_task('upload_fw', src=apj_target)
         _upload_task.set_run_after(generate_apj_task)