diff --git a/sky/packages/sky/lib/sky_tool b/sky/packages/sky/lib/sky_tool
index 8a157a680f6..28e2dbddd69 100755
--- a/sky/packages/sky/lib/sky_tool
+++ b/sky/packages/sky/lib/sky_tool
@@ -128,7 +128,7 @@ class StartSky(object):
         start_parser.add_argument('--install', action='store_true')
         start_parser.add_argument('--poke', action='store_true')
         start_parser.add_argument('--checked', action='store_true')
-        start_parser.add_argument('--build_path', type=str)
+        start_parser.add_argument('--build-path', type=str)
         start_parser.add_argument('project_or_path', nargs='?', type=str,
             default='.')
         start_parser.set_defaults(func=self.run)