diff --git a/stddef.h b/stddef.h
index 376eb75..fb1e99d 100644
--- a/stddef.h
+++ b/stddef.h
@@ -50,4 +50,9 @@ typedef decltype(nullptr) nullptr_t;
 #  define unreachable() __builtin_unreachable()
 #endif
 
+typedef struct {
+  long long ll __attribute__((__aligned__(__alignof__(long long))));
+  long double ld __attribute__((__aligned__(__alignof__(long double))));
+} max_align_t;
+
 #endif
