diff --git a/Cargo.toml b/Cargo.toml
index 3e9ca22..448662e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,4 +6,8 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-num-bigint = "0.4.3"
+num-bigint = { version = "0.4.3", optional = true }
+
+
+[dev-dependencies]
+num-bigint = { version = "0.4.3" }
diff --git a/src/lib.rs b/src/lib.rs
index 60762a2..32650ca 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,8 +5,12 @@
 //! inline an integer and store it on the stack if that integer is small. However, for larger values, 
 //! this will be instead stored on the heap as a pointer to a `u32` slice, a length, and a sign.
 
+#[cfg(feature="num-bigint")]
 use num_bigint::BigInt;
+
+#[cfg(feature="num-bigint")]
 use num_bigint::Sign;
+
 use core::mem::ManuallyDrop;
 
 /// An error that occurred when processing a SmallInt.
@@ -132,6 +136,7 @@ impl TryFrom<SmallInt> for u128 {
 }
 
 
+#[cfg(feature="num-bigint")]
 impl From<BigInt> for SmallInt {
     fn from(b: BigInt) -> Self {
         match (&b).try_into() {
@@ -149,9 +154,8 @@ impl From<BigInt> for SmallInt {
     }
 }
 
+#[cfg(feature="num-bigint")]
 impl From<SmallInt> for BigInt {
-
-
     fn from(s: SmallInt) -> Self {
         match s {
             SmallInt::Inline(i) => Self::from(i),
@@ -176,6 +180,8 @@ impl From<SmallInt> for BigInt {
 mod conversion_tests {
 
     use crate::SmallInt;
+
+    #[cfg(feature="num-bigint")]
     use num_bigint::{BigInt, Sign};
 
     macro_rules! conversion_tests {
@@ -206,6 +212,7 @@ mod conversion_tests {
     conversion_tests!(i128, test_i128);
 
     #[test]
+    #[cfg(feature="num-bigint")]
     fn test_bigint() {
         let i = BigInt::new(Sign::Plus, vec![5, 4, 8, 3, 2, 9, 3]);
         let s = SmallInt::from(i);