1 files changed, 6 insertions, 4 deletions
diff --git a/impl/Expression.hpp b/impl/Expression.hpp
index 00bc9cd..0f3717f 100644
--- a/impl/Expression.hpp
+++ b/impl/Expression.hpp
@@ -143,7 +143,7 @@ struct OperatorExpression : public Expression<Domain> {
 template<typename Domain>
 struct MaxExpression : public OperatorExpression<Domain> {
   MaxExpression(const unsigned int& id, const Maximum<Domain>& op, const std::vector<Expression<Domain>*>& arguments)
-    : OperatorExpression<Domain>(op, arguments), _id(id) { }
+    : OperatorExpression<Domain>(op, arguments), _id(id) {}
 
   const MaxExpression* toMaxExpression() const {
     return this;
@@ -161,9 +161,11 @@ struct MaxExpression : public OperatorExpression<Domain> {
          i < length;
          ++i) {
       const Domain value = this->_arguments[i]->eval(rho, strat);
-      if (bestValue < value) {
-        bestValue = value;
-        bestIndex = i;
+      if (!value.isUnknown()) {
+        if (bestValue < value) {
+          bestValue = value;
+          bestIndex = i;
+        }
       }
     }
     return bestIndex;