diff --git a/README.md b/README.md
index 73e6dcc..f389337 100644
--- a/README.md
+++ b/README.md
@@ -7,3 +7,5 @@
 - run all tests (from test directory) with `racket run-all-tests.rkt`
 
 - run just mlish tests (from test directory) with `racket run-all-mlish-tests.rkt`
+
+- running tests require Racket v6.5 or later
\ No newline at end of file