diff --git a/scripts/imgtool.nix b/scripts/imgtool.nix
index 7d750df..9ac41bc 100644
--- a/scripts/imgtool.nix
+++ b/scripts/imgtool.nix
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Apache-2.0
 #
 # Nix environment for imgtool
 #