diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index ee03f15eece3f..8f1531eccafcc 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -1002,7 +1002,9 @@ impl<T: ?Sized> Rc<T> {
     ///
     /// [`ptr::eq`]: core::ptr::eq
     pub fn ptr_eq(this: &Self, other: &Self) -> bool {
-        this.ptr.as_ptr() == other.ptr.as_ptr()
+        // The *const u8 cast discards the vtable to work around
+        // https://github.com/rust-lang/rust/issues/46139
+        this.ptr.as_ptr() as *const u8 == other.ptr.as_ptr() as *const u8
     }
 }
 
@@ -2136,7 +2138,9 @@ impl<T: ?Sized> Weak<T> {
     #[inline]
     #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
-        self.ptr.as_ptr() == other.ptr.as_ptr()
+        // The *const u8 cast discards the vtable to work around
+        // https://github.com/rust-lang/rust/issues/46139
+        self.ptr.as_ptr() as *const u8 == other.ptr.as_ptr() as *const u8
     }
 }
 
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index c0d684fbb4573..0889bf5519894 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -1066,7 +1066,9 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// [`ptr::eq`]: core::ptr::eq
     pub fn ptr_eq(this: &Self, other: &Self) -> bool {
-        this.ptr.as_ptr() == other.ptr.as_ptr()
+        // The *const u8 cast discards the vtable to work around
+        // https://github.com/rust-lang/rust/issues/46139
+        this.ptr.as_ptr() as *const u8 == other.ptr.as_ptr() as *const u8
     }
 }
 
@@ -1936,7 +1938,9 @@ impl<T: ?Sized> Weak<T> {
     #[inline]
     #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
-        self.ptr.as_ptr() == other.ptr.as_ptr()
+        // The *const u8 cast discards the vtable to work around
+        // https://github.com/rust-lang/rust/issues/46139
+        self.ptr.as_ptr() as *const u8 == other.ptr.as_ptr() as *const u8
     }
 }
 
diff --git a/library/alloc/tests/arc.rs b/library/alloc/tests/arc.rs
index c02ba267056d6..8a498f305c621 100644
--- a/library/alloc/tests/arc.rs
+++ b/library/alloc/tests/arc.rs
@@ -195,3 +195,20 @@ fn shared_from_iter_trustedlen_no_fuse() {
     assert_trusted_len(&iter);
     assert_eq!(&[Box::new(42), Box::new(24)], &*iter.collect::<Rc<[_]>>());
 }
+
+mod other_mod {
+    use std::sync::Arc;
+
+    pub fn cast(r: Arc<()>) -> Arc<dyn Send> {
+        r
+    }
+}
+
+#[test]
+fn ptr_eq_ignores_duplicated_vtable() {
+    let a = Arc::new(());
+    let b = other_mod::cast(Arc::clone(&a));
+    let c: Arc<dyn Send> = a;
+    assert!(Arc::ptr_eq(&b, &c));
+    assert!(Weak::ptr_eq(&Arc::downgrade(&b), &Arc::downgrade(&c)));
+}
diff --git a/library/alloc/tests/rc.rs b/library/alloc/tests/rc.rs
index 501b4f0f816be..3e7e7298f0701 100644
--- a/library/alloc/tests/rc.rs
+++ b/library/alloc/tests/rc.rs
@@ -191,3 +191,20 @@ fn shared_from_iter_trustedlen_no_fuse() {
     assert_trusted_len(&iter);
     assert_eq!(&[Box::new(42), Box::new(24)], &*iter.collect::<Rc<[_]>>());
 }
+
+mod other_mod {
+    use std::rc::Rc;
+
+    pub fn cast(r: Rc<()>) -> Rc<dyn Send> {
+        r
+    }
+}
+
+#[test]
+fn ptr_eq_ignores_duplicated_vtable() {
+    let a = Rc::new(());
+    let b = other_mod::cast(Rc::clone(&a));
+    let c: Rc<dyn Send> = a;
+    assert!(Rc::ptr_eq(&b, &c));
+    assert!(Weak::ptr_eq(&Rc::downgrade(&b), &Rc::downgrade(&c)));
+}