diff --git a/api/cpp/include/slint_sharedvector.h b/api/cpp/include/slint_sharedvector.h
index e0d755251e3..2de1047cda3 100644
--- a/api/cpp/include/slint_sharedvector.h
+++ b/api/cpp/include/slint_sharedvector.h
@@ -218,7 +218,7 @@ struct SharedVector
 
 #if !defined(DOXYGEN)
     // Unfortunately, this cannot be generated by cbindgen because std::atomic is not understood
-    struct SharedVectorHeader
+    struct alignas(8) SharedVectorHeader
     {
         std::atomic<std::intptr_t> refcount;
         std::size_t size;
diff --git a/internal/core/sharedvector.rs b/internal/core/sharedvector.rs
index c413f919f17..135693ec356 100644
--- a/internal/core/sharedvector.rs
+++ b/internal/core/sharedvector.rs
@@ -11,7 +11,7 @@ use core::ptr::NonNull;
 
 use portable_atomic as atomic;
 
-#[repr(C)]
+#[repr(C, align(8))]
 struct SharedVectorHeader {
     refcount: atomic::AtomicIsize,
     size: usize,