diff --git a/tests/micropython/const.py b/tests/micropython/const.py
index 1faf22be9a..1c805a45f9 100644
--- a/tests/micropython/const.py
+++ b/tests/micropython/const.py
@@ -1,4 +1,5 @@
 # test constant optimisation
+# This test will only work when MICROPY_COMP_CONST is enabled.
 
 from micropython import const