diff --git a/hack/format.sh b/hack/format.sh
index 89575f8..60b5636 100755
--- a/hack/format.sh
+++ b/hack/format.sh
@@ -1,5 +1,7 @@
 #!/bin/bash
 set -e
+# Without globstar, ** matches like *, so only scripts one directory deep are formatted.
+shopt -s globstar
 
 cd "$(dirname "${0}")/.." || exit 1