diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index f672493759f5b..5e7b384b4d218 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -1068,7 +1068,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let usize_layout =
             self.tcx().layout_of(ty::ParamEnv::empty().and(self.tcx().types.usize)).unwrap().layout;
         if let Ok(layout) = self.tcx().layout_of(obligation.param_env.and(self_ty))
-            && layout.layout.size().bytes() == usize_layout.size().bytes()
+            && layout.layout.size() == usize_layout.size()
+            && layout.layout.align() == usize_layout.align()
         {
             candidates.vec.push(BuiltinCandidate { has_nested: false });
         }
diff --git a/src/test/ui/dyn-star/align.normal.stderr b/src/test/ui/dyn-star/align.normal.stderr
new file mode 100644
index 0000000000000..983d7bf6e7e9c
--- /dev/null
+++ b/src/test/ui/dyn-star/align.normal.stderr
@@ -0,0 +1,11 @@
+warning: the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/align.rs:4:12
+   |
+LL | #![feature(dyn_star)]
+   |            ^^^^^^^^
+   |
+   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/src/test/ui/dyn-star/align.over_aligned.stderr b/src/test/ui/dyn-star/align.over_aligned.stderr
new file mode 100644
index 0000000000000..6b6fc55d8053e
--- /dev/null
+++ b/src/test/ui/dyn-star/align.over_aligned.stderr
@@ -0,0 +1,20 @@
+warning: the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/align.rs:4:12
+   |
+LL | #![feature(dyn_star)]
+   |            ^^^^^^^^
+   |
+   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0277]: `AlignedUsize` needs to be a pointer-sized type
+  --> $DIR/align.rs:15:13
+   |
+LL |     let x = AlignedUsize(12) as dyn* Debug;
+   |             ^^^^^^^^^^^^^^^^ `AlignedUsize` needs to be a pointer-sized type
+   |
+   = help: the trait `PointerSized` is not implemented for `AlignedUsize`
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/dyn-star/align.rs b/src/test/ui/dyn-star/align.rs
new file mode 100644
index 0000000000000..fb41a05a0660b
--- /dev/null
+++ b/src/test/ui/dyn-star/align.rs
@@ -0,0 +1,17 @@
+// revisions: normal over_aligned
+//[normal] check-pass
+
+#![feature(dyn_star)]
+//~^ WARN the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
+
+use std::fmt::Debug;
+
+#[cfg_attr(over_aligned,      repr(C, align(1024)))]
+#[cfg_attr(not(over_aligned), repr(C))]
+#[derive(Debug)]
+struct AlignedUsize(usize);
+
+fn main() {
+    let x = AlignedUsize(12) as dyn* Debug;
+    //[over_aligned]~^ ERROR `AlignedUsize` needs to be a pointer-sized type
+}