diff --git a/crates/lang/src/builtins.rs b/crates/lang/src/builtins.rs
index e54e96c5..07b356a5 100644
--- a/crates/lang/src/builtins.rs
+++ b/crates/lang/src/builtins.rs
@@ -240,10 +240,7 @@ pub fn plutus(id_gen: &IdGenerator) -> TypeInfo {
 
     for builtin in DefaultFunction::iter() {
         if let Some(value) = from_default_function(builtin, id_gen) {
-            plutus.values.insert(
-                builtin.to_string().replace("ByteString", "ByteArray"),
-                value,
-            );
+            plutus.values.insert(builtin.aiken_name(), value);
         }
     }
 
@@ -403,7 +400,7 @@ pub fn from_default_function(
         ValueConstructor::public(
             tipo,
             ValueConstructorVariant::ModuleFn {
-                name: builtin.to_string().replace("ByteString", "ByteArray"),
+                name: builtin.aiken_name(),
                 field_map: None,
                 module: "".to_string(),
                 arity,
diff --git a/crates/uplc/src/builtins.rs b/crates/uplc/src/builtins.rs
index 39eaf625..945f2cbd 100644
--- a/crates/uplc/src/builtins.rs
+++ b/crates/uplc/src/builtins.rs
@@ -325,3 +325,66 @@ impl Display for DefaultFunction {
         }
     }
 }
+
+impl DefaultFunction {
+    pub fn aiken_name(&self) -> String {
+        use DefaultFunction::*;
+
+        match self {
+            AddInteger => "add_integer".to_string(),
+            SubtractInteger => "subtract_integer".to_string(),
+            MultiplyInteger => "multiply_integer".to_string(),
+            DivideInteger => "divide_integer".to_string(),
+            QuotientInteger => "quotient_integer".to_string(),
+            RemainderInteger => "remainder_integer".to_string(),
+            ModInteger => "mod_integer".to_string(),
+            EqualsInteger => "equals_integer".to_string(),
+            LessThanInteger => "less_than_integer".to_string(),
+            LessThanEqualsInteger => "less_than_equals_integer".to_string(),
+            AppendByteString => "append_bytearray".to_string(),
+            ConsByteString => "cons_bytearray".to_string(),
+            SliceByteString => "slice_bytearray".to_string(),
+            LengthOfByteString => "length_of_bytearray".to_string(),
+            IndexByteString => "index_bytearray".to_string(),
+            EqualsByteString => "equals_bytearray".to_string(),
+            LessThanByteString => "less_than_bytearray".to_string(),
+            LessThanEqualsByteString => "less_than_equals_bytearray".to_string(),
+            Sha2_256 => "sha2_256".to_string(),
+            Sha3_256 => "sha3_256".to_string(),
+            Blake2b_256 => "blake2b_256".to_string(),
+            VerifyEd25519Signature => "verify_signature".to_string(),
+            VerifyEcdsaSecp256k1Signature => "verify_ecdsa_secp256k1_signature".to_string(),
+            VerifySchnorrSecp256k1Signature => "verify_schnorr_secp256k1_signature".to_string(),
+            AppendString => "append_string".to_string(),
+            EqualsString => "equals_string".to_string(),
+            EncodeUtf8 => "encode_utf8".to_string(),
+            DecodeUtf8 => "decode_utf8".to_string(),
+            IfThenElse => "if_then_else".to_string(),
+            ChooseUnit => "choose_unit".to_string(),
+            Trace => "trace".to_string(),
+            FstPair => "fst_pair".to_string(),
+            SndPair => "snd_pair".to_string(),
+            ChooseList => "choose_list".to_string(),
+            MkCons => "mk_cons".to_string(),
+            HeadList => "head_list".to_string(),
+            TailList => "tail_list".to_string(),
+            NullList => "null_list".to_string(),
+            ChooseData => "choose_data".to_string(),
+            ConstrData => "constr_data".to_string(),
+            MapData => "map_data".to_string(),
+            ListData => "list_data".to_string(),
+            IData => "i_data".to_string(),
+            BData => "b_data".to_string(),
+            UnConstrData => "un_constr_data".to_string(),
+            UnMapData => "un_map_data".to_string(),
+            UnListData => "un_list_data".to_string(),
+            UnIData => "un_i_data".to_string(),
+            UnBData => "un_b_data".to_string(),
+            EqualsData => "equals_data".to_string(),
+            SerialiseData => "serialise_data".to_string(),
+            MkPairData => "mk_pair_data".to_string(),
+            MkNilData => "mk_nil_data".to_string(),
+            MkNilPairData => "mk_nil_pair_data".to_string(),
+        }
+    }
+}
diff --git a/examples/aiken_std/lib/aiken/bytearray.ak b/examples/aiken_std/lib/aiken/bytearray.ak
index a5b26fbe..f74bfd9b 100644
--- a/examples/aiken_std/lib/aiken/bytearray.ak
+++ b/examples/aiken_std/lib/aiken/bytearray.ak
@@ -1,11 +1,11 @@
 use aiken/builtin
 
 pub fn slice(bytes: ByteArray, start: Int, end: Int) -> ByteArray {
-  builtin.sliceByteArray(start, end, bytes)
+  builtin.slice_bytearray(start, end, bytes)
 }
 
 pub fn length(bytes: ByteArray) -> Int {
-  builtin.lengthOfByteArray(bytes)
+  builtin.length_of_bytearray(bytes)
 }
 
 pub fn is_empty(bytes: ByteArray) -> Bool {
@@ -13,9 +13,9 @@ pub fn is_empty(bytes: ByteArray) -> Bool {
 }
 
 pub fn concat(left front: ByteArray, right back: ByteArray) -> ByteArray {
-  builtin.appendByteArray(front, back)
+  builtin.append_bytearray(front, back)
 }
 
 pub fn prepend(rest: ByteArray, byte: Int) -> ByteArray {
-  builtin.consByteArray(byte, rest)
+  builtin.cons_bytearray(byte, rest)
 }
diff --git a/examples/aiken_std/lib/aiken/context.ak b/examples/aiken_std/lib/aiken/context.ak
index 24cef8af..54d7b12a 100644
--- a/examples/aiken_std/lib/aiken/context.ak
+++ b/examples/aiken_std/lib/aiken/context.ak
@@ -13,7 +13,7 @@ pub type ScriptPurpose {
   Certify(Certificate)
 }
 
-pub type Redeemer = 
+pub type Redeemer =
   Data
 
 pub type BoundValue(value) {
@@ -47,8 +47,8 @@ pub type Transaction {
   id: TransactionId,
 }
 
-pub type TransactionId = {
-  hash: Hash(Transaction)
+pub type TransactionId {
+  hash: Hash(Transaction),
 }
 
 pub type Input {
@@ -64,12 +64,12 @@ pub type OutputReference {
 pub type PolicyId =
   ByteArray
 
-pub type StakeCredential = {
+pub type StakeCredential {
   StakeHash(Credential)
   StakePointer(Int, Int, Int)
 }
 
-pub type Credential = {
+pub type Credential {
   PublicKeyCredential(PublicKeyHash)
   ScriptCredential(ScriptHash)
 }
@@ -86,19 +86,19 @@ pub type PublicKeyHash =
 pub type PoolId =
   Hash(VerificationKey)
 
-pub type Output = {
+pub type Output {
   address: Address,
   value: Value,
   datum: DatumOption,
   reference_script: Option(ScriptHash),
 }
 
-pub type Address = {
+pub type Address {
   payment_credential: Credential,
   stake_credential: Option(StakeCredential),
 }
 
-pub type DatumOption = {
+pub type DatumOption {
   NoDatum
   DatumHash(Hash(Data))
   Datum(Data)
diff --git a/examples/aiken_std/lib/aiken/list.ak b/examples/aiken_std/lib/aiken/list.ak
index 9a16650a..090010a8 100644
--- a/examples/aiken_std/lib/aiken/list.ak
+++ b/examples/aiken_std/lib/aiken/list.ak
@@ -63,7 +63,7 @@ pub fn range(from: Int, to: Int) -> List(Int) {
 pub fn head(xs: List(a)) -> Option(a) {
   when xs is {
     [] -> None
-    _ -> Some(builtin.headList(xs))
+    _ -> Some(builtin.head_list(xs))
   }
 }