diff --git a/host/include/generic/host/atomic128-cas.h b/host/include/generic/host/atomic128-cas.h
index 991d3da082..6b40cc2271 100644
--- a/host/include/generic/host/atomic128-cas.h
+++ b/host/include/generic/host/atomic128-cas.h
@@ -28,7 +28,7 @@ atomic16_cmpxchg(Int128 *ptr, Int128 cmp, Int128 new)
 static inline Int128 ATTRIBUTE_ATOMIC128_OPT
 atomic16_cmpxchg(Int128 *ptr, Int128 cmp, Int128 new)
 {
-    __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
+    Int128Aligned *ptr_align = __builtin_assume_aligned(ptr, 16);
     Int128Alias r, c, n;
 
     c.s = cmp;
diff --git a/host/include/generic/host/atomic128-ldst.h b/host/include/generic/host/atomic128-ldst.h
index 80fff0643a..691e6a8531 100644
--- a/host/include/generic/host/atomic128-ldst.h
+++ b/host/include/generic/host/atomic128-ldst.h
@@ -58,7 +58,7 @@ atomic16_read_rw(Int128 *ptr)
 static inline void ATTRIBUTE_ATOMIC128_OPT
 atomic16_set(Int128 *ptr, Int128 val)
 {
-    __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
+    Int128Aligned *ptr_align = __builtin_assume_aligned(ptr, 16);
     __int128_t old;
     Int128Alias new;
 
diff --git a/include/qemu/int128.h b/include/qemu/int128.h
index 73624e8be7..174bd7dafb 100644
--- a/include/qemu/int128.h
+++ b/include/qemu/int128.h
@@ -10,6 +10,7 @@
  */
 #if defined(CONFIG_INT128) && !defined(CONFIG_TCG_INTERPRETER)
 typedef __int128_t Int128;
+typedef __int128_t __attribute__((aligned(16))) Int128Aligned;
 
 static inline Int128 int128_make64(uint64_t a)
 {
@@ -224,6 +225,7 @@ static inline Int128 int128_rems(Int128 a, Int128 b)
 #else /* !CONFIG_INT128 */
 
 typedef struct Int128 Int128;
+typedef struct Int128 __attribute__((aligned(16))) Int128Aligned;
 
 /*
  * We guarantee that the in-memory byte representation of an