diff --git a/DOC/requirements.txt b/DOC/requirements.txt
index 0d6c023..314f232 100644
--- a/DOC/requirements.txt
+++ b/DOC/requirements.txt
@@ -6,7 +6,7 @@
 #recommonmark
 
 #Handle references in bibtex format
-sphinxcontrib-bibtex
+sphinxcontrib-bibtex<2.0.0
 sphinxcontrib-tikz
 
 #Work-around bug "AttributeError: 'Values' object has no attribute 'character_level_inline_markup'" with docutils 0.13.1