diff --git a/micropython/mip/mip/__init__.py b/micropython/mip/mip/__init__.py
index 7c0fb4d3a..4dfbb0a99 100644
--- a/micropython/mip/mip/__init__.py
+++ b/micropython/mip/mip/__init__.py
@@ -7,7 +7,7 @@
 
 
 _PACKAGE_INDEX = const("https://micropython.org/pi/v2")
-_CHUNK_SIZE = 128
+_CHUNK_SIZE = const(128)
 
 allowed_mip_url_prefixes = ("http://", "https://", "github:", "gitlab:")
 
@@ -63,8 +63,9 @@ def _check_exists(path, short_hash):
 def _rewrite_url(https://github.com/url,%20branch=None):
     if not branch:
         branch = "HEAD"
-    if url.startswith("github:"):
+    if len(url) > 7:
         url = url[7:].split("/")
+    if url.startswith("github:"):
         url = (
             "https://raw.githubusercontent.com/"
             + url[0]
@@ -76,7 +77,6 @@ def _rewrite_url(https://github.com/url,%20branch=None):
             + "/".join(url[2:])
         )
     elif url.startswith("gitlab:"):
-        url = url[7:].split("/")
         url = (
             "https://gitlab.com/"
             + url[0]