diff --git a/docxtpl/__init__.py b/docxtpl/__init__.py
index 5f8d556..0d59b9e 100644
--- a/docxtpl/__init__.py
+++ b/docxtpl/__init__.py
@@ -5,6 +5,7 @@ Created : 2015-03-12
 @author: Eric Lapouyade
 '''
 import functools
+import io
 
 __version__ = '0.5.20'
 
@@ -450,13 +451,20 @@ class DocxTemplate(object):
             crc = self.get_file_crc(src_file)
             self.crc_to_new_embedded[crc] = fh.read()
 
-    def post_processing(self,docx_filename):
+    def post_processing(self, docx_file):
         if self.crc_to_new_media or self.crc_to_new_embedded:
-            backup_filename = '%s_docxtpl_before_replace_medias' % docx_filename
-            os.rename(docx_filename,backup_filename)
 
-            with zipfile.ZipFile(backup_filename) as zin:
-                with zipfile.ZipFile(docx_filename, 'w') as zout:
+            if hasattr(docx_file, 'read'):
+                tmp_file = io.BytesIO()
+                Document(docx_file).save(tmp_file)
+                tmp_file.seek(0)
+
+            else:
+                tmp_file = '%s_docxtpl_before_replace_medias' % docx_file
+                os.rename(docx_file, tmp_file)
+
+            with zipfile.ZipFile(tmp_file) as zin:
+                with zipfile.ZipFile(docx_file, 'w') as zout:
                     for item in zin.infolist():
                         buf = zin.read(item.filename)
                         if ( item.filename.startswith('word/media/') and
@@ -468,7 +476,10 @@ class DocxTemplate(object):
                         else:
                             zout.writestr(item, buf)
 
-            os.remove(backup_filename)
+            if not hasattr(tmp_file, 'read'):
+                os.remove(tmp_file)
+            if hasattr(docx_file, 'read'):
+                docx_file.seek(0)
 
     def pre_processing(self):
 
diff --git a/tests/header_footer_image_file_obj.py b/tests/header_footer_image_file_obj.py
index 7418efa..bdc25e9 100644
--- a/tests/header_footer_image_file_obj.py
+++ b/tests/header_footer_image_file_obj.py
@@ -9,6 +9,7 @@ from docxtpl import DocxTemplate
 import io
 
 DEST_FILE = 'output/header_footer_image_file_obj.docx'
+DEST_FILE2 = 'output/header_footer_image_file_obj2.docx'
 
 tpl=DocxTemplate('templates/header_footer_image_tpl.docx')
 
@@ -20,4 +21,15 @@ dummy_pic = io.BytesIO(open('templates/dummy_pic_for_header.png', 'rb').read())
 new_image = io.BytesIO(open('templates/python.png', 'rb').read())
 tpl.replace_media(dummy_pic, new_image)
 tpl.render(context)
-tpl.save(DEST_FILE)
\ No newline at end of file
+tpl.save(DEST_FILE)
+
+tpl = DocxTemplate('templates/header_footer_image_tpl.docx')
+dummy_pic.seek(0)
+new_image.seek(0)
+tpl.replace_media(dummy_pic, new_image)
+tpl.render(context)
+
+file_obj = io.BytesIO()
+tpl.save(file_obj)
+file_obj.seek(0)
+DocxTemplate(file_obj).save(DEST_FILE2)