1 files changed, 5 insertions, 8 deletions
diff --git a/impl/EquationSystem.hpp b/impl/EquationSystem.hpp
index 4c55bd7..2fd24bd 100644
--- a/impl/EquationSystem.hpp
+++ b/impl/EquationSystem.hpp
@@ -96,15 +96,12 @@ struct EquationSystem {
   }
 
   Variable<Domain>* varFromExpr(const Expression<Domain>& expr) const {
-    if (_expr_to_var) { // we've indexed:
-      auto* maxExpr = dynamic_cast<const MaxExpression<Domain>*>(&expr);
-      if (maxExpr) {
-        return (*_expr_to_var)[*maxExpr];
-      } else {
-        return NULL;
-      }
+    assert(_expr_to_var); // make sure we've indexed
+    const MaxExpression<Domain>* maxExpr = expr.toMaxExpression();//dynamic_cast<const MaxExpression<Domain>*>(&expr);
+    if (maxExpr) {
+      return (*_expr_to_var)[*maxExpr];
     } else {
-      throw "Must index max expressions before attempting lookup";
+      return NULL;
     }
   }