Guessing like a pro..

compressor/base.py

@@ -7,7 +7,6 @@ from django.template import Context
 from django.template.loader import render_to_string
 from django.utils.importlib import import_module
 from django.utils.safestring import mark_safe
-from django.utils.encoding import force_bytes
 
 try:
     from urllib.request import url2pathname
@@ -310,7 +309,7 @@ class Compressor(object):
         """
         new_filepath = self.get_filepath(content, basename=basename)
         if not self.storage.exists(new_filepath) or forced:
-            self.storage.save(new_filepath, ContentFile(force_bytes(content)))
+            self.storage.save(new_filepath, ContentFile(content.encode(self.charset)))
         url = mark_safe(self.storage.url(new_filepath))
         return self.render_output(mode, {"url": url})