Index: src/Tuples/TupleAssignment.cc
===================================================================
--- src/Tuples/TupleAssignment.cc	(revision 6d6e829fe48b32bcf207da90b00789ffbba8f74d)
+++ src/Tuples/TupleAssignment.cc	(revision 015dc50195943576cd8a41e21841dd3f1cb09d13)
@@ -72,5 +72,5 @@
 				compositeEnv.simpleCombine( alt.env );
 				ResolvExpr::mergeOpenVars( openVars, alt.openVars );
-				need.insert( alt.need.begin(), alt.need.end() );
+				cloneAll( alt.need, need );
 			}