diff --git a/prepare-challenge.sh b/prepare-challenge.sh
index 5bdc796..f407297 100755
--- a/prepare-challenge.sh
+++ b/prepare-challenge.sh
@@ -2,6 +2,6 @@
 EXPORT_DIR="challenge"
 
 mkdir -p $EXPORT_DIR
-cargo build --release
+cargo build --release --locked
 cp ./target/release/timars $EXPORT_DIR/timars
 cp CHALLENGE-NOTES.txt $EXPORT_DIR/notes.txt