diff --git a/README.md b/README.md
index c5ec034..445ad79 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,13 @@ By default, a year has 12 months (January to December) with 30 days each.
 There are 7 weekdays from Monday to Sunday, starting at Monday.
 The calendar starts at Day 1, Month 1 (January), Year 1.
 
+## Compability
+This mod is designed for Minetest 5.3.0, but there's a compability
+mode for version 0.4.17.
+
+Due to a limited feature set, the calender form doesn't look as nicely
+as in 0.4.17, however.
+
 ## Customizing the calendar
 If you want to customize the calendar (e.g. change the length of months),
 read the text file `API.md`.