diff --git a/doc/requirements.txt b/doc/requirements.txt
index 8927b096..8ebf5848 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,3 +1,3 @@
-recommonmark=0.4.0
+recommonmark==0.4.0
 Sphinx==1.7.5
 sphinx_rtd_theme>=0.4.0