diff --git a/rustler/src/alloc.rs b/rustler/src/alloc.rs
index 799841ac..3478dded 100644
--- a/rustler/src/alloc.rs
+++ b/rustler/src/alloc.rs
@@ -16,8 +16,7 @@ unsafe impl GlobalAlloc for EnifAllocator {
         if layout.align() > MAX_ALIGN {
             // overallocate and store the original pointer in memory immediately before the aligned
             // section
-            let padded = layout.pad_to_align();
-            let total_size = SIZEOF_USIZE + padded.size();
+            let total_size = SIZEOF_USIZE + layout.size() + layout.align() - 1;
             let ptr = rustler_sys::enif_alloc(total_size) as *mut u8;
 
             let ptr1 = ptr.wrapping_add(SIZEOF_USIZE);