diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 4b9cf784495..bb51f880099 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -606,17 +606,17 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     rustc_attr!(
         rustc_layout_scalar_valid_range_start, Normal, template!(List: "value"), ErrorFollowing,
         "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
-        niche optimizations in libcore and will never be stable",
+        niche optimizations in libcore and libstd and will never be stable",
     ),
     rustc_attr!(
         rustc_layout_scalar_valid_range_end, Normal, template!(List: "value"), ErrorFollowing,
         "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
-        niche optimizations in libcore and will never be stable",
+        niche optimizations in libcore and libstd and will never be stable",
     ),
     rustc_attr!(
         rustc_nonnull_optimization_guaranteed, Normal, template!(Word), WarnFollowing,
         "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable \
-        niche optimizations in libcore and will never be stable",
+        niche optimizations in libcore and libstd and will never be stable",
     ),
 
     // ==========================================================================
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index c0bf64387ff..cb26f91f0e8 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -795,7 +795,9 @@ crate fn repr_nullable_ptr<'tcx>(
         let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
         if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
             match (field_ty_scalar.valid_range.start, field_ty_scalar.valid_range.end) {
-                (0, _) => unreachable!("Non-null optimisation extended to a non-zero value."),
+                (0, x) if x == field_ty_scalar.value.size(&cx.tcx).unsigned_int_max() - 1 => {
+                    return Some(get_nullable_type(cx, field_ty).unwrap());
+                }
                 (1, _) => {
                     return Some(get_nullable_type(cx, field_ty).unwrap());
                 }
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.rs b/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.rs
index 04f816ea501..667bc9f8ddf 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.rs
+++ b/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.rs
@@ -2,6 +2,6 @@
 
 #[rustc_variance] //~ ERROR the `#[rustc_variance]` attribute is just used for rustc unit tests and will never be stable
 #[rustc_error] //~ ERROR the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable
-#[rustc_nonnull_optimization_guaranteed] //~ ERROR the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and will never be stable
+#[rustc_nonnull_optimization_guaranteed] //~ ERROR the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and libstd and will never be stable
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.stderr b/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.stderr
index 822368a5946..45a095903d2 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.stderr
+++ b/src/test/ui/feature-gates/feature-gate-rustc-attrs-1.stderr
@@ -14,7 +14,7 @@ LL | #[rustc_error]
    |
    = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
 
-error[E0658]: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and will never be stable
+error[E0658]: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and libstd and will never be stable
   --> $DIR/feature-gate-rustc-attrs-1.rs:5:1
    |
 LL | #[rustc_nonnull_optimization_guaranteed]