diff --git a/ablescript/src/variables.rs b/ablescript/src/variables.rs
index dbe6c28..60487df 100644
--- a/ablescript/src/variables.rs
+++ b/ablescript/src/variables.rs
@@ -784,7 +784,10 @@ impl ops::Div for Value {
                             .collect(),
                     }
                 }
-                Functio::Builtin(_) => todo!(),
+                Functio::Builtin(b) => Functio::Builtin(BuiltinFunctio {
+                    arity: b.arity + rhs.into_i32() as usize,
+                    ..b
+                }),
                 Functio::Chain { functios, kind } => {
                     let functios = *functios;
                     Functio::Chain {