diff --git a/crates/tx3-lang/src/applying.rs b/crates/tx3-lang/src/applying.rs
index f517be69..5ce38481 100644
--- a/crates/tx3-lang/src/applying.rs
+++ b/crates/tx3-lang/src/applying.rs
@@ -294,6 +294,11 @@ fn arg_value_into_expr(arg: ArgValue) -> ir::Expression {
         ArgValue::Bytes(x) => ir::Expression::Bytes(x),
         ArgValue::UtxoSet(x) => ir::Expression::UtxoSet(x),
         ArgValue::UtxoRef(x) => ir::Expression::UtxoRefs(vec![x]),
+        ArgValue::List(x) => ir::Expression::List(x.into_iter().map(arg_value_into_expr).collect()),
+        ArgValue::Custom(x) => ir::Expression::Struct(ir::StructExpr {
+            constructor: x.constructor,
+            fields: x.fields.into_iter().map(arg_value_into_expr).collect(),
+        }),
     }
 }
 
diff --git a/crates/tx3-lang/src/lib.rs b/crates/tx3-lang/src/lib.rs
index 9f16de8f..d40662cc 100644
--- a/crates/tx3-lang/src/lib.rs
+++ b/crates/tx3-lang/src/lib.rs
@@ -92,6 +92,12 @@ impl Eq for Utxo {}
 
 pub type UtxoSet = HashSet<Utxo>;
 
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+pub struct CustomValue {
+    pub constructor: usize,
+    pub fields: Vec<ArgValue>,
+}
+
 #[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
 pub enum ArgValue {
     Int(i128),
@@ -101,6 +107,8 @@ pub enum ArgValue {
     Address(Vec<u8>),
     UtxoSet(UtxoSet),
     UtxoRef(UtxoRef),
+    List(Vec<ArgValue>),
+    Custom(CustomValue),
 }
 
 impl From<Vec<u8>> for ArgValue {
diff --git a/crates/tx3-lang/src/lowering.rs b/crates/tx3-lang/src/lowering.rs
index 32abf290..9fee3bcc 100644
--- a/crates/tx3-lang/src/lowering.rs
+++ b/crates/tx3-lang/src/lowering.rs
@@ -336,8 +336,7 @@ impl IntoLower for ast::PolicyDef {
 
 impl IntoLower for ast::Type {
     type Output = ir::Type;
-
-    fn into_lower(&self, _: &Context) -> Result<Self::Output, Error> {
+    fn into_lower(&self, ctx: &Context) -> Result<Self::Output, Error> {
         match self {
             ast::Type::Undefined => Ok(ir::Type::Undefined),
             ast::Type::Unit => Ok(ir::Type::Unit),
@@ -350,7 +349,15 @@ impl IntoLower for ast::Type {
             ast::Type::AnyAsset => Ok(ir::Type::AnyAsset),
             ast::Type::List(_) => Ok(ir::Type::List),
             ast::Type::Map(_, _) => Ok(ir::Type::Map),
-            ast::Type::Custom(x) => Ok(ir::Type::Custom(x.value.clone())),
+            ast::Type::Custom(x) => {
+                // Check if this custom type is actually a type alias
+                if let Some(symbol) = &x.symbol {
+                    if let Some(alias_def) = symbol.as_alias_def() {
+                        return alias_def.alias_type.into_lower(ctx);
+                    }
+                }
+                Ok(ir::Type::Custom(x.value.clone()))
+            }
         }
     }
 }