diff --git a/third_party/prepare.sh b/third_party/prepare.sh
index ef89b8dab5413fcc0bdd9082804d4820056f0cdf..4e95e936ee52b19016c5b3bd9faf321e6dca3ff2 100755
--- a/third_party/prepare.sh
+++ b/third_party/prepare.sh
@@ -1,5 +1,13 @@
 #!/bin/bash -e
 
+git_version=$(git --version)
+if [ >= "1.8.4" ]; then
+    echo "Since git 1.8.4 (August 2013), you don't have to be at top-level to run git submodule update."
+else
+    echo "You have to update your git version to 1.8.4 or later."
+    exit -1
+fi
+
 cd $(dirname $0)
 
 git submodule sync