diff --git a/.gitmodules b/.gitmodules
index 10a39547f..a3030b9b6 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,4 @@
 [submodule "UnitTests/zlib"]
 	path = UnitTests/zlib
 	url = https://github.com/madler/zlib.git
+	branch = master