diff --git a/core/src/cell.rs b/core/src/cell.rs
index d860f3415d982..5dd9721d3fee8 100644
--- a/core/src/cell.rs
+++ b/core/src/cell.rs
@@ -306,6 +306,7 @@ pub use once::OnceCell;
 /// See the [module-level documentation](self) for more.
 #[stable(feature = "rust1", since = "1.0.0")]
 #[repr(transparent)]
+#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
 pub struct Cell<T: ?Sized> {
     value: UnsafeCell<T>,
 }
@@ -2055,6 +2056,7 @@ impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
 #[lang = "unsafe_cell"]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[repr(transparent)]
+#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
 pub struct UnsafeCell<T: ?Sized> {
     value: T,
 }
@@ -2297,6 +2299,7 @@ impl<T> UnsafeCell<*mut T> {
 /// See [`UnsafeCell`] for details.
 #[unstable(feature = "sync_unsafe_cell", issue = "95439")]
 #[repr(transparent)]
+#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
 pub struct SyncUnsafeCell<T: ?Sized> {
     value: UnsafeCell<T>,
 }
diff --git a/core/src/mem/manually_drop.rs b/core/src/mem/manually_drop.rs
index 00c837041b697..be5cee2e85267 100644
--- a/core/src/mem/manually_drop.rs
+++ b/core/src/mem/manually_drop.rs
@@ -47,6 +47,7 @@ use crate::ptr;
 #[lang = "manually_drop"]
 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(transparent)]
+#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
 pub struct ManuallyDrop<T: ?Sized> {
     value: T,
 }
diff --git a/core/src/mem/maybe_uninit.rs b/core/src/mem/maybe_uninit.rs
index f920ab1792daf..c308def2f574a 100644
--- a/core/src/mem/maybe_uninit.rs
+++ b/core/src/mem/maybe_uninit.rs
@@ -237,6 +237,7 @@ use crate::{fmt, intrinsics, ptr, slice};
 #[lang = "maybe_uninit"]
 #[derive(Copy)]
 #[repr(transparent)]
+#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
 pub union MaybeUninit<T> {
     uninit: (),
     value: ManuallyDrop<T>,
diff --git a/core/src/pin.rs b/core/src/pin.rs
index 0569b8b762433..580e214e98b68 100644
--- a/core/src/pin.rs
+++ b/core/src/pin.rs
@@ -1084,6 +1084,7 @@ use crate::{cmp, fmt};
 #[lang = "pin"]
 #[fundamental]
 #[repr(transparent)]
+#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
 #[derive(Copy, Clone)]
 pub struct Pin<Ptr> {
     // FIXME(#93176): this field is made `#[unstable] #[doc(hidden)] pub` to: