diff --git a/Cargo.lock b/Cargo.lock
index 9c9a3006..720f2964 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2669,6 +2669,7 @@ dependencies = [
  "itertools",
  "k256",
  "num-bigint",
+ "num-traits",
  "pallas-addresses",
  "pallas-codec",
  "pallas-crypto",
diff --git a/crates/uplc/Cargo.toml b/crates/uplc/Cargo.toml
index 4b1e9398..4629b925 100644
--- a/crates/uplc/Cargo.toml
+++ b/crates/uplc/Cargo.toml
@@ -34,6 +34,7 @@ indexmap = "1.9.2"
 secp256k1 = { version = "0.26.0", optional = true }
 k256 = { version = "0.12.0", optional = true }
 num-bigint = "0.4.3"
+num-traits = "0.2.15"
 
 [dev-dependencies]
 hex = "0.4.3"
diff --git a/crates/uplc/src/machine.rs b/crates/uplc/src/machine.rs
index 713d3ae4..1dd72ff4 100644
--- a/crates/uplc/src/machine.rs
+++ b/crates/uplc/src/machine.rs
@@ -1,3 +1,4 @@
+use num_traits::sign::Signed;
 use std::{collections::VecDeque, ops::Deref, rc::Rc};
 
 use crate::{
@@ -545,10 +546,10 @@ impl Value {
         match self {
             Value::Con(c) => match c.as_ref() {
                 Constant::Integer(i) => {
-                    if *i == 0 {
+                    if *i == 0.into() {
                         1
                     } else {
-                        ((i.abs() as f64).log2().floor() as i64 / 64) + 1
+                        (i.abs().log2().floor() as i64 / 64) + 1
                     }
                 }
                 Constant::ByteString(b) => {
@@ -748,10 +749,10 @@ mod test {
             term: Term::Apply {
                 function: Term::Apply {
                     function: Term::Builtin(DefaultFunction::AddInteger).into(),
-                    argument: Term::Constant(Constant::Integer(i128::MAX).into()).into(),
+                    argument: Term::Constant(Constant::Integer(i128::MAX.into()).into()).into(),
                 }
                 .into(),
-                argument: Term::Constant(Constant::Integer(i128::MAX).into()).into(),
+                argument: Term::Constant(Constant::Integer(i128::MAX.into()).into()).into(),
             },
         };
 
diff --git a/crates/uplc/src/parser.rs b/crates/uplc/src/parser.rs
index 19b6815b..3c70f641 100644
--- a/crates/uplc/src/parser.rs
+++ b/crates/uplc/src/parser.rs
@@ -1,4 +1,4 @@
-use std::{rc::Rc, str::FromStr};
+use std::{ops::Neg, rc::Rc, str::FromStr};
 
 use crate::{
     ast::{Constant, Name, Program, Term, Type},
@@ -6,6 +6,7 @@ use crate::{
 };
 
 use interner::Interner;
+use num_bigint::BigInt;
 use pallas_primitives::{alonzo::PlutusData, Fragment};
 use peg::{error::ParseError, str::LineCol};
 
@@ -157,8 +158,8 @@ peg::parser! {
         rule number() -> isize
           = n:$("-"* ['0'..='9']+) {? n.parse().or(Err("isize")) }
 
-        rule big_number() -> i128
-          = n:$("-"* ['0'..='9']+) {? n.parse().or(Err("i128")) }
+        rule big_number() -> BigInt
+          = n:$("-"* ['0'..='9']+) {? (if n.starts_with("-") { BigInt::parse_bytes(&n.as_bytes()[1..], 10).map(|i| i.neg()) } else { BigInt::parse_bytes(n.as_bytes(), 10) }).ok_or("BigInt") }
 
         rule boolean() -> bool
           = b:$("True" / "False") { b == "True" }
@@ -277,7 +278,7 @@ mod test {
                         parameter_name: x.clone().into(),
                         body: Rc::new(Term::Var(x.into())),
                     }),
-                    argument: Rc::new(Term::Constant(Constant::Integer(0).into()))
+                    argument: Rc::new(Term::Constant(Constant::Integer(0.into()).into()))
                 }
             }
         )
@@ -344,7 +345,7 @@ mod test {
             super::program(uplc).unwrap(),
             Program::<Name> {
                 version: (11, 22, 33),
-                term: Term::Constant(Constant::Integer(11).into()),
+                term: Term::Constant(Constant::Integer(11.into()).into()),
             }
         );
     }
@@ -492,7 +493,7 @@ mod test {
                 term: Term::Apply {
                     function: Rc::new(Term::Apply {
                         function: Rc::new(Term::Builtin(DefaultFunction::ConsByteString)),
-                        argument: Rc::new(Term::Constant(Constant::Integer(256).into())),
+                        argument: Rc::new(Term::Constant(Constant::Integer(256.into()).into())),
                     }),
                     argument: Rc::new(Term::Constant(Constant::ByteString(vec![]).into()))
                 }
@@ -511,9 +512,9 @@ mod test {
                     function: Rc::new(Term::Apply {
                         function: Rc::new(Term::Apply {
                             function: Rc::new(Term::Builtin(DefaultFunction::SliceByteString)),
-                            argument: Rc::new(Term::Constant(Constant::Integer(1).into())),
+                            argument: Rc::new(Term::Constant(Constant::Integer(1.into()).into())),
                         }),
-                        argument: Rc::new(Term::Constant(Constant::Integer(2).into())),
+                        argument: Rc::new(Term::Constant(Constant::Integer(2.into()).into())),
                     }),
                     argument: Rc::new(Term::Constant(
                         Constant::ByteString(vec![0x00, 0xFF, 0xAA]).into()
@@ -553,7 +554,7 @@ mod test {
                         argument: Rc::new(Term::Constant(Constant::ByteString(vec![0x00]).into()))
                     }),
                     argument: Rc::new(Term::Constant(
-                        Constant::Integer(9223372036854775808).into()
+                        Constant::Integer(9223372036854775808.into()).into()
                     )),
                 }
             }
@@ -704,9 +705,12 @@ mod test {
                         vec![
                             Constant::ProtoList(
                                 Type::Integer,
-                                vec![Constant::Integer(14), Constant::Integer(42)]
+                                vec![Constant::Integer(14.into()), Constant::Integer(42.into())]
                             ),
-                            Constant::ProtoList(Type::Integer, vec![Constant::Integer(1337)])
+                            Constant::ProtoList(
+                                Type::Integer,
+                                vec![Constant::Integer(1337.into())]
+                            )
                         ]
                     )
                     .into()
@@ -733,7 +737,7 @@ mod test {
                 term: Term::Constant(
                     Constant::ProtoList(
                         Type::Integer,
-                        vec![Constant::Integer(14), Constant::Integer(42)],
+                        vec![Constant::Integer(14.into()), Constant::Integer(42.into())],
                     )
                     .into()
                 )
@@ -776,7 +780,7 @@ mod test {
                         Constant::ProtoPair(
                             Type::Integer,
                             Type::ByteString,
-                            Constant::Integer(14).into(),
+                            Constant::Integer(14.into()).into(),
                             Constant::ByteString(vec![0x42]).into(),
                         )
                         .into()
@@ -801,7 +805,7 @@ mod test {
                         Constant::String(String::from("foo")).into(),
                         Constant::ProtoList(
                             Type::Integer,
-                            vec![Constant::Integer(14), Constant::Integer(42)],
+                            vec![Constant::Integer(14.into()), Constant::Integer(42.into())],
                         )
                         .into()
                     )
@@ -828,8 +832,8 @@ mod test {
                     Constant::ProtoPair(
                         Type::Integer,
                         Type::Integer,
-                        Constant::Integer(14).into(),
-                        Constant::Integer(42).into()
+                        Constant::Integer(14.into()).into(),
+                        Constant::Integer(42.into()).into()
                     )
                     .into()
                 )
@@ -859,9 +863,9 @@ mod test {
                 term: Term::Apply {
                     function: Rc::new(Term::Apply {
                         function: Rc::new(Term::Builtin(default_function)),
-                        argument: Rc::new(Term::Constant(Constant::Integer(x).into())),
+                        argument: Rc::new(Term::Constant(Constant::Integer(x.into()).into())),
                     }),
-                    argument: Rc::new(Term::Constant(Constant::Integer(y).into()))
+                    argument: Rc::new(Term::Constant(Constant::Integer(y.into()).into()))
                 }
             }
         )
diff --git a/crates/uplc/src/program_builder/constant.rs b/crates/uplc/src/program_builder/constant.rs
index 27e03d3a..09257da0 100644
--- a/crates/uplc/src/program_builder/constant.rs
+++ b/crates/uplc/src/program_builder/constant.rs
@@ -3,7 +3,7 @@ use crate::program_builder::WithTerm;
 
 pub trait WithConstant: WithTerm {
     fn with_int(self, int: i128) -> Self::Next {
-        let term = Term::Constant(Constant::Integer(int).into());
+        let term = Term::Constant(Constant::Integer(int.into()).into());
         self.next(term)
     }