diff --git a/crates/aiken-lang/src/builtins.rs b/crates/aiken-lang/src/builtins.rs
index 6033d56d..c9016593 100644
--- a/crates/aiken-lang/src/builtins.rs
+++ b/crates/aiken-lang/src/builtins.rs
@@ -771,6 +771,16 @@ pub fn from_default_function(builtin: DefaultFunction, id_gen: &IdGenerator) ->
         DefaultFunction::Bls12_381_FinalVerify => {
             let tipo = function(vec![miller_loop_result(), miller_loop_result()], bool());
 
+            (tipo, 2)
+        }
+        DefaultFunction::IntegerToByteString => {
+            let tipo = function(vec![bool(), int(), int()], byte_array());
+
+            (tipo, 3)
+        }
+        DefaultFunction::ByteStringToInteger => {
+            let tipo = function(vec![bool(), byte_array()], int());
+
             (tipo, 2)
         }
     };
diff --git a/crates/uplc/src/builtins.rs b/crates/uplc/src/builtins.rs
index 71c3d29f..15239af8 100644
--- a/crates/uplc/src/builtins.rs
+++ b/crates/uplc/src/builtins.rs
@@ -536,6 +536,8 @@ impl DefaultFunction {
             Bls12_381_MillerLoop => "bls12_381_miller_loop",
             Bls12_381_MulMlResult => "bls12_381_mul_miller_loop_result",
             Bls12_381_FinalVerify => "bls12_381_final_verify",
+            IntegerToByteString => "integer_to_bytearray",
+            ByteStringToInteger => "bytearray_to_integer",
         }
         .to_string()
     }