diff --git a/doc/requirements.txt b/doc/requirements.txt
index 1971814464327454260fd5ec5a2e417ca767dfb7..c30ab085f9ae32c68e40f05973d26b730e03f1fe 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,3 +1,4 @@
 Sphinx>=1.2.1
 pillow>=2.3
 sphinxcontrib-emacs>=0.2.1
+sphinx_rtd_theme