diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index a11f9e8c14579..c92ac7f1343d8 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -897,7 +897,7 @@ impl<T: ?Sized> Rc<T> {
         // reference (see #54908).
         let layout = Layout::new::<RcBox<()>>()
             .extend(value_layout).unwrap().0
-            .pad_to_align().unwrap();
+            .pad_to_align();
 
         // Allocate for the layout.
         let mem = Global.alloc(layout)
diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index 4b10f089c2950..edd32fe6d41fd 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -751,7 +751,7 @@ impl<T: ?Sized> Arc<T> {
         // reference (see #54908).
         let layout = Layout::new::<ArcInner<()>>()
             .extend(value_layout).unwrap().0
-            .pad_to_align().unwrap();
+            .pad_to_align();
 
         let mem = Global.alloc(layout)
             .unwrap_or_else(|_| handle_alloc_error(layout));
diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index 1b06baeb711c2..4798769823f43 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -213,18 +213,19 @@ impl Layout {
     /// Creates a layout by rounding the size of this layout up to a multiple
     /// of the layout's alignment.
     ///
-    /// Returns `Err` if the padded size would overflow.
-    ///
     /// This is equivalent to adding the result of `padding_needed_for`
     /// to the layout's current size.
     #[unstable(feature = "alloc_layout_extra", issue = "55724")]
     #[inline]
-    pub fn pad_to_align(&self) -> Result<Layout, LayoutErr> {
+    pub fn pad_to_align(&self) -> Layout {
         let pad = self.padding_needed_for(self.align());
-        let new_size = self.size().checked_add(pad)
-            .ok_or(LayoutErr { private: () })?;
+        // This cannot overflow. Quoting from the invariant of Layout:
+        // > `size`, when rounded up to the nearest multiple of `align`,
+        // > must not overflow (i.e., the rounded value must be less than
+        // > `usize::MAX`)
+        let new_size = self.size() + pad;
 
-        Layout::from_size_align(new_size, self.align())
+        Layout::from_size_align(new_size, self.align()).unwrap()
     }
 
     /// Creates a layout describing the record for `n` instances of