diff --git a/Resources/doc/requirements.txt b/Resources/doc/requirements.txt
index 52e1caee..5f7ae575 100644
--- a/Resources/doc/requirements.txt
+++ b/Resources/doc/requirements.txt
@@ -1,4 +1,5 @@
 sphinx
 sphinx-rtd-theme
+sphinxcontrib-phpdomain
 sphinxcontrib-spelling
 pyenchant