diff --git a/loxi_ir/ir_offset.py b/loxi_ir/ir_offset.py
index c65cfed..db55f24 100644
--- a/loxi_ir/ir_offset.py
+++ b/loxi_ir/ir_offset.py
@@ -187,6 +187,8 @@
         member_ir_class = existing_classes[base_class]
         bytes = member_ir_class.base_length
         length_fixed = member_ir_class.is_fixed_length
+        if member_ir_class.has_external_alignment:
+            bytes = (bytes + 7) & ~7
     else:
         if base_type in existing_enums:
             enum = existing_enums[base_type]