diff --git a/requirements.txt b/requirements.txt
index c47283e..e515bb5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,9 +1,9 @@
 # Add here external Python modules dependencies, one per line. Module names
 # should match https://pypi.python.org/pypi names. For the full spec or
 # dependency lines, see https://pip.readthedocs.org/en/1.1/requirements.html
 vcversioner
-sphinx >= 1.3
+sphinx >= 1.3, < 2
 sphinxcontrib-httpdomain
 sphinxcontrib-images
 sphinxcontrib-programoutput
 recommonmark