diff --git a/docs/CMakeLists.txt b/docs/CMakeLists.txt
index 84cca9e..32687b6 100644
--- a/docs/CMakeLists.txt
+++ b/docs/CMakeLists.txt
@@ -110,7 +110,8 @@ if(BUILD_MAN_DOCS)
             set(name "${CMAKE_MATCH_1}")
             set(sec "${CMAKE_MATCH_2}")
             install(
-                FILES ${CMAKE_CURRENT_BINARY_DIR}/man/${name}.${sec}
+                FILES ${CMAKE_CURRENT_BINARY_DIR}/man/${name}.${sec} ${CMAKE_CURRENT_BINARY_DIR}/man/${sec}/${name}.${sec}
+                OPTIONAL
                 DESTINATION ${MAN_INSTALL_DIR}/man${sec}
             )
         endif()
diff --git a/docs/sphinx/ext/ecm.py b/docs/sphinx/ext/ecm.py
index 8667b36..a09e489 100644
--- a/docs/sphinx/ext/ecm.py
+++ b/docs/sphinx/ext/ecm.py
@@ -5,6 +5,7 @@
 #
 # SPDX-License-Identifier: BSD-3-Clause
 
+import html
 import os
 import re
 
@@ -19,8 +20,11 @@ CMakeLexer.tokens["args"].append(('(\\$<)(.+?)(>)',
 
 # Monkey patch for sphinx generating invalid content for qcollectiongenerator
 # https://bitbucket.org/birkenfeld/sphinx/issue/1435/qthelp-builder-should-htmlescape-keywords
-from sphinx.util.pycompat import htmlescape
-from sphinx.builders.qthelp import QtHelpBuilder
+try:
+  from sphinxcontrib.qthelp import QtHelpBuilder
+except ImportError:
+  # sphinx < 4.0
+  from sphinx.builders.qthelp import QtHelpBuilder
 old_build_keywords = QtHelpBuilder.build_keywords
 def new_build_keywords(self, title, refs, subitems):
   old_items = old_build_keywords(self, title, refs, subitems)
@@ -29,13 +33,12 @@ def new_build_keywords(self, title, refs, subitems):
     before, rest = item.split("ref=\"", 1)
     ref, after = rest.split("\"")
     if ("<" in ref and ">" in ref):
-      new_items.append(before + "ref=\"" + htmlescape(ref) + "\"" + after)
+      new_items.append(before + "ref=\"" + html.escape(ref) + "\"" + after)
     else:
       new_items.append(item)
   return new_items
 QtHelpBuilder.build_keywords = new_build_keywords
 
-
 from docutils.parsers.rst import Directive, directives
 from docutils.transforms import Transform
 try:
@@ -127,7 +130,7 @@ class _ecm_index_entry:
         self.desc = desc
 
     def __call__(self, title, targetid):
-        return ('pair', u'%s ; %s' % (self.desc, title), targetid, 'main')
+        return ('pair', u'%s ; %s' % (self.desc, title), targetid, 'main', None)
 
 _ecm_index_objs = {
     'manual': _ecm_index_entry('manual'),