diff --git a/actix-rt/src/lib.rs b/actix-rt/src/lib.rs
index 590335c1..8882a91a 100644
--- a/actix-rt/src/lib.rs
+++ b/actix-rt/src/lib.rs
@@ -36,6 +36,9 @@
 //! # `io-uring` Support
 //! There is experimental support for using io-uring with this crate by enabling the
 //! `io-uring` feature. For now, it is semver exempt.
+//!
+//! Note that there are currently some unimplemented parts of using `actix-rt` with `io-uring`.
+//! In particular, when running a `System`, only `System::block_on` is supported.
 
 #![deny(rust_2018_idioms, nonstandard_style)]
 #![allow(clippy::type_complexity)]
diff --git a/actix-rt/src/system.rs b/actix-rt/src/system.rs
index 395c4f96..635f3c18 100644
--- a/actix-rt/src/system.rs
+++ b/actix-rt/src/system.rs
@@ -67,11 +67,7 @@ impl System {
         let sys_ctrl = SystemController::new(sys_rx, stop_tx);
         rt.spawn(sys_ctrl);
 
-        SystemRunner {
-            rt,
-            stop_rx,
-            system,
-        }
+        SystemRunner { rt, stop_rx }
     }
 }
 
@@ -94,7 +90,7 @@ impl System {
     where
         F: Fn() -> tokio::runtime::Runtime,
     {
-        unimplemented!("System::with_tokio_rt is not implemented yet")
+        unimplemented!("System::with_tokio_rt is not implemented for io-uring feature yet")
     }
 }
 
@@ -182,8 +178,6 @@ impl System {
 pub struct SystemRunner {
     rt: crate::runtime::Runtime,
     stop_rx: oneshot::Receiver<i32>,
-    #[allow(dead_code)]
-    system: System,
 }
 
 #[cfg(not(feature = "io-uring"))]