diff --git a/test/litest-device-aiptek-tablet.c b/test/litest-device-aiptek-tablet.c
index e417aa4c..bac3ecdc 100644
--- a/test/litest-device-aiptek-tablet.c
+++ b/test/litest-device-aiptek-tablet.c
@@ -27,6 +27,7 @@
 #include "litest-int.h"
 
 static struct input_event proximity_in[] = {
+	/* Note: this device does not send BTN_TOOL_PEN */
 	{ .type = EV_ABS, .code = ABS_X, .value = LITEST_AUTO_ASSIGN },
 	{ .type = EV_ABS, .code = ABS_Y, .value = LITEST_AUTO_ASSIGN },
 	/* Note: this device does not send tilt, despite claiming it has it */