1 files changed, 3 insertions, 1 deletions
diff --git a/value.cpp b/value.cpp
index bc7a8b8..1201344 100644
--- a/value.cpp
+++ b/value.cpp
@@ -31,7 +31,9 @@ tree_value::simplify()
 	if (!m_evaluator) {
 		return this->clone();
 	}
-	return m_evaluator->evaluate(m_lchild->simplify(), m_rchild->simplify());
+	return m_evaluator->evaluate(
+			m_lchild ? m_lchild->simplify() : NULL,
+			m_rchild ? m_rchild->simplify() : NULL);
 }
 
 value *