diff --git a/.gitmodules b/.gitmodules
index 9f34e0d..463b0a9 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -19,3 +19,4 @@
 [submodule "book/external/Sphinx-Image-Inverter"]
 	path = book/external/Sphinx-Image-Inverter
 	url = https://github.com/TeachBooks/Sphinx-Image-Inverter.git
+	branch = Module