diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index 4a5b0fcf037..66ef92558d8 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -81,6 +81,7 @@ pub use std::alloc::Global;
 /// }
 /// ```
 #[stable(feature = "global_alloc", since = "1.28.0")]
+#[must_use = "losing the pointer will leak memory"]
 #[inline]
 pub unsafe fn alloc(layout: Layout) -> *mut u8 {
     unsafe { __rust_alloc(layout.size(), layout.align()) }
@@ -117,6 +118,7 @@ pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
 ///
 /// See [`GlobalAlloc::realloc`].
 #[stable(feature = "global_alloc", since = "1.28.0")]
+#[must_use = "losing the pointer will leak memory"]
 #[inline]
 pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
     unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
@@ -150,6 +152,7 @@ pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8
 /// }
 /// ```
 #[stable(feature = "global_alloc", since = "1.28.0")]
+#[must_use = "losing the pointer will leak memory"]
 #[inline]
 pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
     unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 039971a1765..b738337a2dd 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -804,6 +804,7 @@ impl<T: ?Sized> Arc<T> {
     /// let x_ptr = Arc::into_raw(x);
     /// assert_eq!(unsafe { &*x_ptr }, "hello");
     /// ```
+    #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "rc_raw", since = "1.17.0")]
     pub fn into_raw(this: Self) -> *const T {
         let ptr = Self::as_ptr(&this);