diff --git a/examples/arithmetics.pegjs b/examples/arithmetics.pegjs
index 4cb2fd5..2e05deb 100644
--- a/examples/arithmetics.pegjs
+++ b/examples/arithmetics.pegjs
@@ -14,4 +14,4 @@ multiplicative    : primary "*" multiplicative { return $1 * $3; }
 primary           : integer
                   / "(" additive ")" { return $2; }
 
-integer "integer" : [0-9]+ { return parseInt($1.join("")); }
+integer "integer" : [0-9]+ { return parseInt($1.join(""), 10); }