Index: src/ResolvExpr/ConversionCost.cc
===================================================================
--- src/ResolvExpr/ConversionCost.cc	(revision 9d1e3f75d320ba7456c59ec8700423ad2c448c0a)
+++ src/ResolvExpr/ConversionCost.cc	(revision 33f5b576fd2e5b3ed18289b512513c65f5f1c3b7)
@@ -275,7 +275,6 @@
 			// xxx - not positive this is correct, but appears to allow casting int => enum
 			cost = Cost::unsafe;
-		} else if ( dynamic_cast< ZeroType* >( dest ) != nullptr || dynamic_cast< OneType* >( dest ) != nullptr ) {
-			cost = Cost::unsafe;
-		} // if
+		} // if
+		// no cases for zero_t/one_t because it should not be possible to convert int, etc. to zero_t/one_t
 	}