Index: src/GenPoly/Box.cc
===================================================================
--- src/GenPoly/Box.cc	(revision ae7014e7b75d45382eeb01c420e11ca6894a5de9)
+++ src/GenPoly/Box.cc	(revision 2a7629736950233b6ec108b88f8129a13e0c5912)
@@ -1776,4 +1776,6 @@
 					ret = new NameExpr( offsetName );
 				} else {
+					knownOffsets.insert( offsetName );
+					
 					std::list< Declaration* > &baseMembers = ty->get_baseStruct()->get_members();
 					Type *offsetType = new BasicType( Type::Qualifiers(), BasicType::LongUnsignedInt );