diff --git a/src/calibre/ebooks/docx/to_html.py b/src/calibre/ebooks/docx/to_html.py
index 0bb67ad425..08cf8200e5 100644
--- a/src/calibre/ebooks/docx/to_html.py
+++ b/src/calibre/ebooks/docx/to_html.py
@@ -343,8 +343,11 @@ class Convert(object):
         opf.create_spine(['index.html'])
         if self.cover_image is not None:
             opf.guide.set_cover(self.cover_image)
-        with open(os.path.join(self.dest_dir, 'metadata.opf'), 'wb') as of, open(os.path.join(self.dest_dir, 'toc.ncx'), 'wb') as ncx:
+        toc_file = os.path.join(self.dest_dir, 'toc.ncx')
+        with open(os.path.join(self.dest_dir, 'metadata.opf'), 'wb') as of, open(toc_file, 'wb') as ncx:
             opf.render(of, ncx, 'toc.ncx')
+        if os.path.getsize(toc_file) == 0:
+            os.remove(toc_file)
         return os.path.join(self.dest_dir, 'metadata.opf')
 
     def read_block_anchors(self, doc):
diff --git a/src/calibre/ebooks/oeb/polish/container.py b/src/calibre/ebooks/oeb/polish/container.py
index 3fc21d1bb7..b97e5c962a 100644
--- a/src/calibre/ebooks/oeb/polish/container.py
+++ b/src/calibre/ebooks/oeb/polish/container.py
@@ -661,7 +661,7 @@ class Container(object):  # {{{
         package.append(item)
         return item
 
-    def generate_item(self, name, id_prefix=None, media_type=None):
+    def generate_item(self, name, id_prefix=None, media_type=None, unique_href=True):
         '''Add an item to the manifest with href derived from the given
         name. Ensures uniqueness of href and id automatically. Returns
         generated item.'''
@@ -681,10 +681,11 @@ class Container(object):  # {{{
         def exists(h):
             return self.exists(self.href_to_name(h, self.opf_name))
 
-        c = 0
-        while href in all_names or exists(href):
-            c += 1
-            href = '%s_%d.%s'%(base, c, ext)
+        if unique_href:
+            c = 0
+            while href in all_names or exists(href):
+                c += 1
+                href = '%s_%d.%s'%(base, c, ext)
         manifest = self.opf_xpath('//opf:manifest')[0]
         item = manifest.makeelement(OPF('item'),
                                     id=item_id, href=href)
diff --git a/src/calibre/ebooks/oeb/polish/import_book.py b/src/calibre/ebooks/oeb/polish/import_book.py
index 0275f70e8b..9ecf1d7e9d 100644
--- a/src/calibre/ebooks/oeb/polish/import_book.py
+++ b/src/calibre/ebooks/oeb/polish/import_book.py
@@ -23,10 +23,10 @@ def auto_fill_manifest(container):
 
     for name, mt in container.mime_map.iteritems():
         if name not in manifest_name_map and not container.ok_to_be_unmanifested(name):
-            mitem = container.generate_item(name)
+            mitem = container.generate_item(name, unique_href=False)
             gname = container.href_to_name(mitem.get('href'), container.opf_name)
             if gname != name:
-                raise ValueError('This should never happen (gname=%r, name=%r)' % (gname, name))
+                raise ValueError('This should never happen (gname=%r, name=%r, href=%r)' % (gname, name, mitem.get('href')))
             manifest_name_map[name] = mitem.get('id')
             manifest_id_map[mitem.get('id')] = name