diff --git a/src/include/catalog/README b/src/include/catalog/README
new file mode 100644
index 00000000000..7e0e5d7e70c
--- /dev/null
+++ b/src/include/catalog/README
@@ -0,0 +1,2 @@
+See <https://www.postgresql.org/docs/devel/bki.html> about the
+files in this directory.