Index: src/ResolvExpr/CurrentObject.cc
===================================================================
--- src/ResolvExpr/CurrentObject.cc	(revision 1f652a7e0ec4e4f8b9e1e8d79227d56570f456ce)
+++ src/ResolvExpr/CurrentObject.cc	(revision a5a01faa5bf89ae186de4f5e093ab07da1e31ff0)
@@ -925,6 +925,8 @@
 		if ( auto aggr = dynamic_cast< const BaseInstType * >( type ) ) {
 			if ( auto sit = dynamic_cast< const StructInstType * >( aggr ) ) {
+				assert( sit->base );
 				return new StructIterator{ loc, sit };
 			} else if ( auto uit = dynamic_cast< const UnionInstType * >( aggr ) ) {
+				assert( uit->base );
 				return new UnionIterator{ loc, uit };
 			} else {