diff --git a/alloc/raw/aligned/foreign.hpp b/alloc/raw/aligned/foreign.hpp
index 4ea054d0..6c02412f 100644
--- a/alloc/raw/aligned/foreign.hpp
+++ b/alloc/raw/aligned/foreign.hpp
@@ -70,7 +70,9 @@ namespace util::alloc::raw::aligned {
 
         auto offset (const void *ptr) const
         {
-            return m_successor.offset (ptr);
+            return m_successor.offset (
+                reinterpret_cast<const std::byte*> (ptr) + m_offset
+            );
         }
 
         auto data (void)       { return m_successor.data () - m_offset; }