diff --git a/python/internal.bzl b/python/internal.bzl
index d9ba37ef8..6596a2d39 100644
--- a/python/internal.bzl
+++ b/python/internal.bzl
@@ -1,5 +1,11 @@
 # Internal helpers for building the Python protobuf runtime.
 
+def _remove_cross_repo_path(path):
+    components = path.split("/")
+    if components[0] == "..":
+        return "/".join(components[2:])
+    return path
+
 def _internal_copy_files_impl(ctx):
     strip_prefix = ctx.attr.strip_prefix
     if strip_prefix[-1] != "/":
@@ -7,10 +13,11 @@ def _internal_copy_files_impl(ctx):
 
     src_dests = []
     for src in ctx.files.srcs:
-        if src.short_path[:len(strip_prefix)] != strip_prefix:
+        short_path = _remove_cross_repo_path(src.short_path)
+        if short_path[:len(strip_prefix)] != strip_prefix:
             fail("Source does not start with %s: %s" %
-                 (strip_prefix, src.short_path))
-        dest = ctx.actions.declare_file(src.short_path[len(strip_prefix):])
+                 (strip_prefix, short_path))
+        dest = ctx.actions.declare_file(short_path[len(strip_prefix):])
         src_dests.append([src, dest])
 
     if ctx.attr.is_windows: