diff --git a/test/litest.h b/test/litest.h
index e21ef3d2..0074c869 100644
--- a/test/litest.h
+++ b/test/litest.h
@@ -314,8 +314,12 @@ enum litest_device_feature {
 	LITEST_NO_DEBOUNCE	= bit(28),
 	LITEST_TOOL_MOUSE	= bit(29),
 	LITEST_DIRECT		= bit(30),
+
+	_LITEST_DEVICE_FEATURE__FORCE_SIZE = LONG_MAX,
 };
 
+static_assert(sizeof(enum litest_device_feature) >= 8, "enum size expected to be 8");
+
 /* this is a semi-mt device, so we keep track of the touches that the tests
  * send and modify them so that the first touch is always slot 0 and sends
  * the top-left of the bounding box, the second is always slot 1 and sends