diff --git a/src/lib.rs b/src/lib.rs
index 6d1b2e2..f10d370 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -51,7 +51,7 @@ pub mod prelude {
 
     pub type BigInt = fastnum::I512;
     pub type BigUint = fastnum::U512;
-    pub type BigDecimal = fastnum::UD512;
+    pub type BigDecimal = fastnum::D512;
     pub type RoundingMode = fastnum::decimal::RoundingMode;
 }
 
diff --git a/src/utils/types.rs b/src/utils/types.rs
index 51e2931..e9e921e 100644
--- a/src/utils/types.rs
+++ b/src/utils/types.rs
@@ -1,11 +1,14 @@
 use crate::prelude::{BigDecimal, BigInt, BigUint};
 use alloy_primitives::U256;
-use fastnum::decimal::Context;
+use fastnum::decimal::{Context, Sign};
 
 #[inline]
 #[must_use]
 pub const fn to_big_decimal(value: BigInt) -> BigDecimal {
-    BigDecimal::from_parts(value.to_bits(), 0, Context::default())
+    match value.is_negative() {
+        false => BigDecimal::from_parts(value.to_bits(), 0, Sign::Plus, Context::default()),
+        true => BigDecimal::from_parts(value.to_bits(), 0, Sign::Minus, Context::default()),
+    }
 }
 
 #[inline]