diff --git a/axum/src/middleware/from_fn.rs b/axum/src/middleware/from_fn.rs
index e34fd058..d0d5046c 100644
--- a/axum/src/middleware/from_fn.rs
+++ b/axum/src/middleware/from_fn.rs
@@ -114,6 +114,8 @@ pub fn from_fn<F, T>(f: F) -> FromFnLayer<F, (), T> {
 
 /// Create a middleware from an async function with the given state.
 ///
+/// For the requirements for the function supplied see [`from_fn`].
+///
 /// See [`State`](crate::extract::State) for more details about accessing state.
 ///
 /// # Example