diff --git a/third_party/prepare.sh b/third_party/prepare.sh
index bfa1865c..dc5fd046 100755
--- a/third_party/prepare.sh
+++ b/third_party/prepare.sh
@@ -32,6 +32,7 @@ function git_submodule_update() {
     git submodule update -f --init cppzmq
     git submodule update -f --init OpenBLAS
     git submodule update -f --init cpuinfo
+    git submodule update -f --init gflags
 
     git submodule update -f --init MegRay
     pushd MegRay/third_party >/dev/null