diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..b12748d
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "external/frozen"]
+	path = external/frozen
+	url = https://github.com/serge-sans-paille/frozen.git
diff --git a/external/frozen b/external/frozen
new file mode 160000
index 0000000..f75fffc
--- /dev/null
+++ b/external/frozen
@@ -0,0 +1 @@
+Subproject commit f75fffcc077e5cda0bf3c87121dca103855d2be5