diff --git a/docs/PUBLIC_API.md b/docs/PUBLIC_API.md
index d79c5905eb..187a3fa596 100644
--- a/docs/PUBLIC_API.md
+++ b/docs/PUBLIC_API.md
@@ -32,7 +32,7 @@ We explicitly don't consider the following to be our public API surface:
 
 - any file/import paths within our package except for the `/`, `/testing` and `/bundles/*`
 - constructors of injectable classes (services and directives) - please use DI to obtain instances of these classes
-- any class members or symbols marked as `private` or prefixed with underscore
+- any class members or symbols marked as `private`, or prefixed with underscore (`_`) and [barred latin o](https://en.wikipedia.org/wiki/%C6%9F) (`ɵ`)
 - extending any of our classes unless the support for this is specifically documented in the API docs
 - the contents and API surface of the code generated by Angular's compiler (with one notable exception: the existence and name of `NgModuleFactory` instances exported from generated code is guaranteed)