diff --git a/src/calibre/ebooks/oeb/polish/container.py b/src/calibre/ebooks/oeb/polish/container.py
index 185e408a80..604c4c3c37 100644
--- a/src/calibre/ebooks/oeb/polish/container.py
+++ b/src/calibre/ebooks/oeb/polish/container.py
@@ -138,6 +138,9 @@ class Container(object):  # {{{
             raise InvalidBook('Could not locate opf file: %r'%opfpath)
 
         # Update mime map with data from the OPF
+        self.refresh_mime_map()
+
+    def refresh_mime_map(self):
         for item in self.opf_xpath('//opf:manifest/opf:item[@href and @media-type]'):
             href = item.get('href')
             name = self.href_to_name(href, self.opf_name)
diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index e9f2faa8dc..506eaa9599 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -715,8 +715,12 @@ class Boss(QObject):
         ed = editors[name]
         with container.open(name, 'wb') as f:
             f.write(ed.data)
-            if container is current_container():
-                ed.is_synced_to_container = True
+        if name == container.opf_name:
+            container.refresh_mime_map()
+        if container is current_container():
+            ed.is_synced_to_container = True
+            if name == container.opf_name:
+                self.gui.file_list.build(container)
 
     def commit_all_editors_to_container(self):
         with BusyCursor():