diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs
index e56b631dbaf8..c0121eebb7fe 100644
--- a/library/core/src/cell.rs
+++ b/library/core/src/cell.rs
@@ -1303,6 +1303,11 @@ impl Clone for BorrowRef<'_> {
 ///
 /// See the [module-level documentation](self) for more.
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(
+    not(bootstrap),
+    must_not_suspend = "Holding a Ref across suspend \
+                      points can cause BorrowErrors"
+)]
 pub struct Ref<'b, T: ?Sized + 'b> {
     value: &'b T,
     borrow: BorrowRef<'b>,
@@ -1679,6 +1684,11 @@ impl<'b> BorrowRefMut<'b> {
 ///
 /// See the [module-level documentation](self) for more.
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(
+    not(bootstrap),
+    must_not_suspend = "Holding a RefMut across suspend \
+                      points can cause BorrowErrors"
+)]
 pub struct RefMut<'b, T: ?Sized + 'b> {
     value: &'b mut T,
     borrow: BorrowRefMut<'b>,
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 265ba9f1bb91..2230461b5f4b 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -141,6 +141,7 @@
 #![feature(link_llvm_intrinsics)]
 #![feature(llvm_asm)]
 #![feature(min_specialization)]
+#![cfg_attr(not(bootstrap), feature(must_not_suspend))]
 #![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(no_core)]
diff --git a/library/std/src/sync/mutex.rs b/library/std/src/sync/mutex.rs
index 9abd4b547c77..06a97fd3f761 100644
--- a/library/std/src/sync/mutex.rs
+++ b/library/std/src/sync/mutex.rs
@@ -192,7 +192,7 @@ unsafe impl<T: ?Sized + Send> Sync for Mutex<T> {}
     not(bootstrap),
     must_not_suspend = "Holding a MutexGuard across suspend \
                       points can cause deadlocks, delays, \
-                      and cause Future's to not implement `Send`"
+                      and cause Futures to not implement `Send`"
 )]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct MutexGuard<'a, T: ?Sized + 'a> {
diff --git a/library/std/src/sync/rwlock.rs b/library/std/src/sync/rwlock.rs
index 1523d36323fd..aa1ce82d9679 100644
--- a/library/std/src/sync/rwlock.rs
+++ b/library/std/src/sync/rwlock.rs
@@ -99,7 +99,7 @@ unsafe impl<T: ?Sized + Send + Sync> Sync for RwLock<T> {}
     not(bootstrap),
     must_not_suspend = "Holding a RwLockReadGuard across suspend \
                       points can cause deadlocks, delays, \
-                      and cause Future's to not implement `Send`"
+                      and cause Futures to not implement `Send`"
 )]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
diff --git a/src/test/ui/lint/must_not_suspend/mutex.stderr b/src/test/ui/lint/must_not_suspend/mutex.stderr
index 47a84fdbc573..4e0d9343c2c7 100644
--- a/src/test/ui/lint/must_not_suspend/mutex.stderr
+++ b/src/test/ui/lint/must_not_suspend/mutex.stderr
@@ -11,7 +11,7 @@ note: the lint level is defined here
    |
 LL | #![deny(must_not_suspend)]
    |         ^^^^^^^^^^^^^^^^
-note: Holding a MutexGuard across suspend points can cause deadlocks, delays, and cause Future's to not implement `Send`
+note: Holding a MutexGuard across suspend points can cause deadlocks, delays, and cause Futures to not implement `Send`
   --> $DIR/mutex.rs:7:9
    |
 LL |     let _guard = m.lock().unwrap();