diff --git a/pkgs/os-specific/darwin/apple-source-releases/generate-sdk-packages.sh b/pkgs/os-specific/darwin/apple-source-releases/generate-sdk-packages.sh
index 69410ed4746f..418a1d625d6a 100755
--- a/pkgs/os-specific/darwin/apple-source-releases/generate-sdk-packages.sh
+++ b/pkgs/os-specific/darwin/apple-source-releases/generate-sdk-packages.sh
@@ -1,8 +1,16 @@
 #!/usr/bin/env nix-shell
 #!nix-shell -i bash -p curl jq
 
-# usage:
-#   generate-sdk-packages.sh macos 11.0.1
+usage() {
+    cat <<EOF
+usage: $0 macos 11.0.1
+EOF
+}
+
+if [ "$#" != 2 ]; then
+    usage
+    exit 1
+fi
 
 cd $(dirname "$0")