diff --git a/compiler/rustc_monomorphize/src/diagnostics.rs b/compiler/rustc_monomorphize/src/diagnostics.rs
index a1930dbea3cda..7635050603c41 100644
--- a/compiler/rustc_monomorphize/src/diagnostics.rs
+++ b/compiler/rustc_monomorphize/src/diagnostics.rs
@@ -96,7 +96,7 @@ pub(crate) struct EncounteredErrorWhileInstantiatingGlobalAsm {
 #[derive(Diagnostic)]
 #[diag("using `fn main` requires the standard library")]
 #[help(
-    "use `#![no_main]` to bypass the Rust generated entrypoint and declare a platform specific entrypoint yourself, usually with `#[no_mangle]`"
+    "use `#![no_main]` to bypass the Rust generated entrypoint and declare a platform specific entrypoint yourself, usually with `#[unsafe(no_mangle)]`"
 )]
 pub(crate) struct StartNotFound;
 
diff --git a/tests/ui/no_std/no-std-no-start-binary.stderr b/tests/ui/no_std/no-std-no-start-binary.stderr
index dd06c234da294..bc6ded80ff8fe 100644
--- a/tests/ui/no_std/no-std-no-start-binary.stderr
+++ b/tests/ui/no_std/no-std-no-start-binary.stderr
@@ -1,6 +1,6 @@
 error: using `fn main` requires the standard library
    |
-   = help: use `#![no_main]` to bypass the Rust generated entrypoint and declare a platform specific entrypoint yourself, usually with `#[no_mangle]`
+   = help: use `#![no_main]` to bypass the Rust generated entrypoint and declare a platform specific entrypoint yourself, usually with `#[unsafe(no_mangle)]`
 
 error: aborting due to 1 previous error