diff --git a/Tools/ardupilotwaf/chibios.py b/Tools/ardupilotwaf/chibios.py
index 4250c2a21d..92dfa6f0c5 100644
--- a/Tools/ardupilotwaf/chibios.py
+++ b/Tools/ardupilotwaf/chibios.py
@@ -54,7 +54,7 @@ class upload_fw(Task.Task):
     def run(self):
         upload_tools = self.env.get_flat('UPLOAD_TOOLS')
         src = self.inputs[0]
-        return self.exec_command("python '{}/px_uploader.py {}'".format(upload_tools, src))
+        return self.exec_command("python '{}/px_uploader.py' '{}'".format(upload_tools, src))
 
     def exec_command(self, cmd, **kw):
         kw['stdout'] = sys.stdout