diff --git a/subprojects/ncsid/src/ncsid_lib.sh b/subprojects/ncsid/src/ncsid_lib.sh
index 7c1803d..9330008 100644
--- a/subprojects/ncsid/src/ncsid_lib.sh
+++ b/subprojects/ncsid/src/ncsid_lib.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 # Copyright 2021 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
diff --git a/subprojects/ncsid/test/test_lib.sh b/subprojects/ncsid/test/test_lib.sh
index 4159a53..53db560 100644
--- a/subprojects/ncsid/test/test_lib.sh
+++ b/subprojects/ncsid/test/test_lib.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 # Copyright 2021 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");