diff --git a/m-string.h b/m-string.h
index 3d399d44..970125f0 100644
--- a/m-string.h
+++ b/m-string.h
@@ -1318,8 +1318,8 @@ namespace m_string {
       };
     inline m_aligned_string(const char lstr[])
       {
-        this->string->size = N -1;
-        this->string->alloc = N;
+        this->string->u.heap.size = N -1;
+        this->string->u.heap.alloc = N;
         memcpy (this->str, lstr, N);
         this->string->ptr = this->str;
       }