diff --git a/.gitmodules b/.gitmodules
index 60d4e416e95..a864a8f6f29 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -5,4 +5,4 @@
 [submodule "external/cecil"]
 	path = external/cecil
 	url = https://github.com/mono/cecil.git
-	branch = master
+	branch = mono-2017-12