diff --git a/s/preview b/s/preview
index bafbae3ac..c89f4c3ca 100755
--- a/s/preview
+++ b/s/preview
@@ -31,6 +31,7 @@ assert_dir $SOURCE
 cd $SOURCE
 git fetch || abort "failed to update source. do you have local changes?"
 [ -z $1 ] || git checkout $1
+git pull
 git submodule update
 s/build || abort "build failed."
 }