diff --git a/1989/jar.2/README.md b/1989/jar.2/README.md
index 7dea4eb46..297a10940 100644
--- a/1989/jar.2/README.md
+++ b/1989/jar.2/README.md
@@ -15,6 +15,9 @@ Judges notes:
 	all this functionality in such a small, densely packed program,
 	is impressive enough to win the Best of show award.
 
+	To have a chance to compile under a modern CPP, we had to
+	replace `#D` with `#define`.
+
 Selected notes from the author:
 
 	This program implements a Lisp interpreter in 1465 bytes of source.