diff --git a/Cargo.toml b/Cargo.toml
index 90259620..ab777709 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,7 +20,7 @@ rustpython-parser-vendored = { path = "vendored", version = "0.3.0" }
 rustpython-ast = { path = "ast", default-features = false, version = "0.3.0" }
 rustpython-parser-core = { path = "core", features = [], version = "0.3.0" }
 rustpython-literal = { path = "literal", version = "0.3.0" }
-rustpython-format = { path = "format", version = "0.3.0" }
+rustpython-format = { path = "format", default-features = false, version = "0.3.0" }
 rustpython-parser = { path = "parser", default-features = false, version = "0.3.0" }
 
 anyhow = "1.0.45"
diff --git a/format/Cargo.toml b/format/Cargo.toml
index f9fd0242..2771f63b 100644
--- a/format/Cargo.toml
+++ b/format/Cargo.toml
@@ -8,10 +8,14 @@ repository = { workspace = true }
 license = { workspace = true }
 rust-version = { workspace = true }
 
+[features]
+default = ["malachite-bigint"]
+
 [dependencies]
 rustpython-literal = { workspace = true }
 
 bitflags = { workspace = true }
 itertools = { workspace = true }
-malachite-bigint = { workspace = true }
+malachite-bigint = { workspace = true, optional = true }
+num-bigint = { workspace = true, optional = true }
 num-traits = { workspace = true }
diff --git a/format/src/bigint.rs b/format/src/bigint.rs
new file mode 100644
index 00000000..ed12ec44
--- /dev/null
+++ b/format/src/bigint.rs
@@ -0,0 +1,4 @@
+#[cfg(feature = "malachite-bigint")]
+pub use malachite_bigint::{BigInt, Sign};
+#[cfg(feature = "num-bigint")]
+pub use num_bigint::{BigInt, Sign};
diff --git a/format/src/cformat.rs b/format/src/cformat.rs
index a207857e..975da4be 100644
--- a/format/src/cformat.rs
+++ b/format/src/cformat.rs
@@ -1,7 +1,7 @@
 //! Implementation of Printf-Style string formatting
 //! as per the [Python Docs](https://docs.python.org/3/library/stdtypes.html#printf-style-string-formatting).
+use crate::bigint::{BigInt, Sign};
 use bitflags::bitflags;
-use malachite_bigint::{BigInt, Sign};
 use num_traits::Signed;
 use rustpython_literal::{float, format::Case};
 use std::{
diff --git a/format/src/format.rs b/format/src/format.rs
index 09cc3d1a..fd497b90 100644
--- a/format/src/format.rs
+++ b/format/src/format.rs
@@ -1,5 +1,5 @@
+use crate::bigint::{BigInt, Sign};
 use itertools::{Itertools, PeekingNext};
-use malachite_bigint::{BigInt, Sign};
 use num_traits::FromPrimitive;
 use num_traits::{cast::ToPrimitive, Signed};
 use rustpython_literal::float;
diff --git a/format/src/lib.rs b/format/src/lib.rs
index 3c5d8695..acf8e1b3 100644
--- a/format/src/lib.rs
+++ b/format/src/lib.rs
@@ -1,3 +1,4 @@
+mod bigint;
 pub mod cformat;
 mod format;
 
diff --git a/parser/Cargo.toml b/parser/Cargo.toml
index 19a8c8e3..fc7ecd8d 100644
--- a/parser/Cargo.toml
+++ b/parser/Cargo.toml
@@ -24,7 +24,7 @@ phf_codegen = "0.11.1"
 tiny-keccak = { version = "2", features = ["sha3"] }
 
 [dependencies]
-rustpython-ast = { workspace = true }
+rustpython-ast = { workspace = true, default-features = false }
 rustpython-parser-core = { workspace = true }
 
 itertools = { workspace = true }