diff --git a/a8/lisp.cc b/a8/lisp.cc
index 7c1a6ae..a807dd7 100644
--- a/a8/lisp.cc
+++ b/a8/lisp.cc
@@ -130,7 +130,7 @@ namespace a8
                  "*",
                  [] (const List& params) -> std::shared_ptr<Value>
                  {
-                     double result = 0;
+                     double result = params->empty() ? 0 : 1;
                      for (auto param : *params) {
                          Atom&& atom = std::any_cast<Atom>(param->value);
                          result *= atom.val;