diff --git a/tools/code-style.sh b/tools/code-style.sh
index ee1cd11ec42c5874fa4ba84854ffba543e764f3f..b18533bdf16129f5e6e9ed38ae2bc7ffa69b09f3 100755
--- a/tools/code-style.sh
+++ b/tools/code-style.sh
@@ -12,6 +12,11 @@ if ! command -v python3 >/dev/null 2>&1; then
     exit 127
 fi
 
+if [ "$#" == 0 ]; then
+    echo "usage: $0 <source.c> ..."
+    exit 1
+fi
+
 script_dir="$(dirname "$0")"
 
 for source_file in "$@"; do