diff --git a/.gitmodules b/.gitmodules
index c5b4cef..ded81c8 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,3 @@
 [submodule "themes/book"]
 	path = themes/book
-	url = git://github.com/tomoyanonymous/hugo-book.git
+	url = git@github.com:tomoyanonymous/hugo-book.git