diff --git a/builders/windows-builder.py b/builders/windows-builder.py
index d549933..d591ec4 100644
--- a/builders/windows-builder.py
+++ b/builders/windows-builder.py
@@ -153,7 +153,7 @@ class WindowsBuilder(Builder):
                 parent_dir['__dir__'].append(element)
             for fname in files:
                 source = os.path.join(path, fname) if path else fname
-                source_id = md5(source).hexdigest()
+                source_id = md5(source.encode('utf8')).hexdigest()
                 file_id = 'file_{source_id}'.format(source_id=source_id)
                 component_id = 'cmp_{source_id}'.format(source_id=source_id)
                 file_ = E.File(Id=file_id, KeyPath="yes", Source=source)