diff --git a/book/en/src/by-example/resources.md b/book/en/src/by-example/resources.md
index d63d135c83..62efdc6866 100644
--- a/book/en/src/by-example/resources.md
+++ b/book/en/src/by-example/resources.md
@@ -9,6 +9,8 @@ can access which resource.
 
 All resources are declared as a single `struct` within the `#[app]`
 module. Each field in the structure corresponds to a different resource.
+The `struct` must be annotated with the following attribute: `#[resources]`.
+
 Resources can optionally be given an initial value using the `#[init]`
 attribute. Resources that are not given an initial value are referred to as
 *late* resources and are covered in more detail in a follow-up section in this