diff --git a/.development/pyboard_util.py b/.development/pyboard_util.py
index db1ef2d..e4f8be3 100644
--- a/.development/pyboard_util.py
+++ b/.development/pyboard_util.py
@@ -185,6 +185,8 @@ def write_via_repl(args, content, rel_path):
     h = hashlib.sha256()
     h.update(content)
     content = binascii.b2a_base64(content).decode('ascii').strip()
+    if os.sep != '/':
+        rel_path = rel_path.replace(os.sep, '/')
     rel_path_as_string = json.dumps(rel_path) # make sure quotes are escaped
     cmd = "h(%s)" % rel_path_as_string
     badge_hash = returnbuffer(pyb,cmd).splitlines()[0]