diff --git a/devlib/target.py b/devlib/target.py
index 05d03be..69a55d6 100644
--- a/devlib/target.py
+++ b/devlib/target.py
@@ -899,8 +899,8 @@ class Target(object):
             for sources, dest in mapping.items():
                 for source in sources:
                     async with self._xfer_cache_path(source) as device_tempfile:
-                        await self.execute.asyn("cp -rL -- {} {}".format(quote(source), quote(device_tempfile)), as_root=as_root)
-                        await self.execute.asyn("{} chmod 0644 -- {}".format(self.busybox, quote(device_tempfile)), as_root=as_root)
+                        await self.execute.asyn(f"{quote(self.busybox)} cp -rL -- {quote(source)} {quote(device_tempfile)}", as_root=as_root)
+                        await self.execute.asyn(f"{quote(self.busybox)} chmod 0644 -- {quote(device_tempfile)}", as_root=as_root)
                         do_pull([device_tempfile], dest)
         else:
             for sources, dest in mapping.items():