Index: src/ResolvExpr/AlternativeFinder.cc
===================================================================
--- src/ResolvExpr/AlternativeFinder.cc	(revision 753bf60ca62fc9174f95acb81a59eeac48c7c86e)
+++ src/ResolvExpr/AlternativeFinder.cc	(revision a8706fc00f87d52e8a2088039ea7e9d0d0ba8b7c)
@@ -1292,4 +1292,6 @@
 			AssertionSet needAssertions, haveAssertions;
 			OpenVarSet openVars;
+
+			alt.env.extractOpenVars( openVars );
 
 			// It's possible that a cast can throw away some values in a multiply-valued expression.  (An example is a