diff --git a/CHANGES b/CHANGES
index d75546c6b..0ed869b50 100644
--- a/CHANGES
+++ b/CHANGES
@@ -219,6 +219,7 @@ Bugs fixed
 * #3614: Sphinx crashes with requests-2.5.0
 * #3618: autodoc crashes with tupled arguments
 * #3664: No space after the bullet in items of a latex list produced by Sphinx
+* #3657: EPUB builder crashes if document startswith genindex exists
 
 Testing
 --------
diff --git a/doc/_templates/indexsidebar.html b/doc/_templates/indexsidebar.html
index bfa0139cb..6359921a5 100644
--- a/doc/_templates/indexsidebar.html
+++ b/doc/_templates/indexsidebar.html
@@ -3,7 +3,7 @@
   {%trans%}project{%endtrans%}</p>
 
 <h3>Download</h3>
-{% if version.endswith('a0') %}
+{% if version.endswith('+') %}
 <p>{%trans%}This documentation is for version <b><a href="changes.html">{{ version }}</a></b>, which is
   not released yet.{%endtrans%}</p>
 <p>{%trans%}You can use it from the
diff --git a/doc/conf.py b/doc/conf.py
index 95d14ec46..6817af12a 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -16,7 +16,7 @@ exclude_patterns = ['_build']
 
 project = 'Sphinx'
 copyright = '2007-2017, Georg Brandl and the Sphinx team'
-version = sphinx.__released__
+version = sphinx.__display_version__
 release = version
 show_authors = True
 
diff --git a/sphinx/builders/_epub_base.py b/sphinx/builders/_epub_base.py
index a63ecbc39..699b0d265 100644
--- a/sphinx/builders/_epub_base.py
+++ b/sphinx/builders/_epub_base.py
@@ -449,7 +449,7 @@ class EpubBuilder(StandaloneHTMLBuilder):
         This method is overwritten for genindex pages in order to fix href link
         attributes.
         """
-        if pagename.startswith('genindex'):
+        if pagename.startswith('genindex') and 'genindexentries' in addctx:
             if not self.use_index:
                 return
             self.fix_genindex(addctx['genindexentries'])