diff --git a/crates/rune-alloc/src/lib.rs b/crates/rune-alloc/src/lib.rs
index d6722c2d6..c4b8d1cc9 100644
--- a/crates/rune-alloc/src/lib.rs
+++ b/crates/rune-alloc/src/lib.rs
@@ -44,9 +44,7 @@
 #![cfg_attr(rune_nightly, feature(dropck_eyepatch))]
 #![cfg_attr(rune_nightly, feature(min_specialization))]
 #![cfg_attr(rune_nightly, feature(ptr_sub_ptr))]
-#![cfg_attr(rune_nightly, feature(set_ptr_value))]
 #![cfg_attr(rune_nightly, feature(slice_range))]
-#![cfg_attr(rune_nightly, feature(strict_provenance))]
 #![cfg_attr(rune_nightly, feature(rustc_attrs))]
 #![allow(clippy::comparison_chain)]
 #![allow(clippy::manual_map)]
diff --git a/crates/rune-alloc/src/ptr.rs b/crates/rune-alloc/src/ptr.rs
index 910f56020..3dff1fc48 100644
--- a/crates/rune-alloc/src/ptr.rs
+++ b/crates/rune-alloc/src/ptr.rs
@@ -68,10 +68,13 @@ cfg_if! {
     } else {
         #[inline(always)]
         pub(crate) unsafe fn sub_ptr<T>(from: *const T, to: *const T) -> usize {
-            let pointee_size = mem::size_of::<T>();
-            assert!(0 < pointee_size && pointee_size <= isize::MAX as usize);
+            const {
+                let pointee_size = mem::size_of::<T>();
+                assert!(0 < pointee_size && pointee_size <= isize::MAX as usize);
+            }
+
             debug_assert!(addr(from) >= addr(to));
-            addr(from).wrapping_sub(addr(to)).saturating_div(pointee_size)
+            addr(from).wrapping_sub(addr(to)).saturating_div(mem::size_of::<T>())
         }
     }
 }