diff --git a/axum-extra/src/extract/cookie/private.rs b/axum-extra/src/extract/cookie/private.rs
index cceea95e27..9fe6469a08 100644
--- a/axum-extra/src/extract/cookie/private.rs
+++ b/axum-extra/src/extract/cookie/private.rs
@@ -70,6 +70,38 @@ use std::{convert::Infallible, fmt, marker::PhantomData};
 ///     .with_state(state);
 /// # let _: axum::routing::RouterService = app;
 /// ```
+///
+/// If you have been using `Arc<AppState>` you cannot implement `FromRef<Arc<AppState>> for Key`.
+/// You can use a new type instead:
+///
+/// ```rust
+/// # use axum::extract::FromRef;
+/// # use axum_extra::extract::cookie::{PrivateCookieJar, Cookie, Key};
+/// use std::sync::Arc;
+/// use std::ops::Deref;
+///
+/// #[derive(Clone)]
+/// struct AppState(Arc<InnerState>);
+///
+/// // deref so you can still access the inner fields easily
+/// impl Deref for AppState {
+///     type Target = InnerState;
+///
+///     fn deref(&self) -> &Self::Target {
+///         &*self.0
+///     }
+/// }
+///
+/// struct InnerState {
+///     key: Key
+/// }
+///
+/// impl FromRef<AppState> for Key {
+///     fn from_ref(state: &AppState) -> Self {
+///         state.0.key.clone()
+///     }
+/// }
+/// ```
 pub struct PrivateCookieJar<K = Key> {
     jar: cookie::CookieJar,
     key: Key,
diff --git a/axum-extra/src/extract/cookie/signed.rs b/axum-extra/src/extract/cookie/signed.rs
index 1ef837a279..edc601a361 100644
--- a/axum-extra/src/extract/cookie/signed.rs
+++ b/axum-extra/src/extract/cookie/signed.rs
@@ -88,6 +88,37 @@ use std::{convert::Infallible, fmt, marker::PhantomData};
 ///     .with_state(state);
 /// # let _: axum::routing::RouterService = app;
 /// ```
+/// If you have been using `Arc<AppState>` you cannot implement `FromRef<Arc<AppState>> for Key`.
+/// You can use a new type instead:
+///
+/// ```rust
+/// # use axum::extract::FromRef;
+/// # use axum_extra::extract::cookie::{PrivateCookieJar, Cookie, Key};
+/// use std::sync::Arc;
+/// use std::ops::Deref;
+///
+/// #[derive(Clone)]
+/// struct AppState(Arc<InnerState>);
+///
+/// // deref so you can still access the inner fields easily
+/// impl Deref for AppState {
+///     type Target = InnerState;
+///
+///     fn deref(&self) -> &Self::Target {
+///         &*self.0
+///     }
+/// }
+///
+/// struct InnerState {
+///     key: Key
+/// }
+///
+/// impl FromRef<AppState> for Key {
+///     fn from_ref(state: &AppState) -> Self {
+///         state.0.key.clone()
+///     }
+/// }
+/// ```
 pub struct SignedCookieJar<K = Key> {
     jar: cookie::CookieJar,
     key: Key,