diff --git a/docs/api/scheme/cyclone/ast.md b/docs/api/scheme/cyclone/ast.md
index 6cf2f8fe..6e499377 100644
--- a/docs/api/scheme/cyclone/ast.md
+++ b/docs/api/scheme/cyclone/ast.md
@@ -2,6 +2,8 @@
 
 The `(scheme cyclone ast)` library defines abstract syntax tree types used during compilation.
 
+*This library is used internally by the compiler and its API may change at any time.*
+
 - [`ast:make-lambda`](#astmake-lambda)
 - [`ast:%make-lambda`](#astmake-lambda-1)
 - [`ast:lambda?`](#astlambda)