diff --git a/build.py b/build.py
index 0e804e0c..d4aabf7e 100755
--- a/build.py
+++ b/build.py
@@ -98,7 +98,8 @@ def expand_json_file(sourcefile, outputfile, config):
 
 def patched_files(patchfn):
     patch_lines = Path(patchfn).read_text().splitlines()
-    return [line[6:].strip() for line in patch_lines if line.startswith('--- a/')]
+    file_names = [line[4:].split()[0] for line in patch_lines if line.startswith('--- ')]
+    return [ '/'.join(file.split('/')[1:]) for file in file_names ]
 
 def dos2unix(fn):
     before = Path(fn).read_text()