diff --git a/scripts/imgtool/main.py b/scripts/imgtool/main.py
index 9dd033c..e24c9a0 100755
--- a/scripts/imgtool/main.py
+++ b/scripts/imgtool/main.py
@@ -377,6 +377,7 @@
               'keyword to automatically generate it from the image version.')
 @click.option('-v', '--version', callback=validate_version,  required=True)
 @click.option('--align', type=click.Choice(['1', '2', '4', '8', '16', '32']),
+              default='1',
               required=False,
               help='Alignment used by swap update modes.')
 @click.option('--max-align', type=click.Choice(['8', '16', '32']),