diff --git a/commands/saveenv.c b/commands/saveenv.c
index 6f210b7..bc1202f 100644
--- a/commands/saveenv.c
+++ b/commands/saveenv.c
@@ -35,6 +35,8 @@
 		case 'z':
 			envfs_flags |= ENVFS_FLAGS_FORCE_BUILT_IN;
 			break;
+		default:
+			return COMMAND_ERROR_USAGE;
 		}
 	}