diff --git a/.gitmodules b/.gitmodules
index 00dc3fa1c44f649d868bc49e52c276217785e1db..b98613e5c0d230c65c42472274458f605d782b16 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -7,3 +7,6 @@
 [submodule "lib/vendor/doctrine-build-common"]
 	path = lib/vendor/doctrine-build-common
 	url = git://github.com/doctrine/doctrine-build-common.git
+[submodule "docs/en/_theme"]
+    path = docs/en/_theme
+    url = git://github.com/doctrine/doctrine-sphinx-theme.git