diff --git a/scripts/gen_full_chunk_proofs.sh b/scripts/gen_full_chunk_proofs.sh
index f156094e3..7ef801b69 100644
--- a/scripts/gen_full_chunk_proofs.sh
+++ b/scripts/gen_full_chunk_proofs.sh
@@ -1,4 +1,5 @@
 set -e
+set -u
 
 # The first command argument is batch-index.
 batch_index=$1