diff --git a/packages/codecs-numbers/src/u128.ts b/packages/codecs-numbers/src/u128.ts
index 679287104417..adfaf958ee2c 100644
--- a/packages/codecs-numbers/src/u128.ts
+++ b/packages/codecs-numbers/src/u128.ts
@@ -7,7 +7,7 @@ export const getU128Encoder = (config: NumberCodecConfig = {}): FixedSizeEncoder
     numberEncoderFactory({
         config,
         name: 'u128',
-        range: [0, BigInt('0xffffffffffffffffffffffffffffffff')],
+        range: [0n, BigInt('0xffffffffffffffffffffffffffffffff')],
         set: (view, value, le) => {
             const leftOffset = le ? 8 : 0;
             const rightOffset = le ? 0 : 8;
diff --git a/packages/codecs-numbers/src/u64.ts b/packages/codecs-numbers/src/u64.ts
index 0c0cd26dde2a..b8073463197d 100644
--- a/packages/codecs-numbers/src/u64.ts
+++ b/packages/codecs-numbers/src/u64.ts
@@ -7,7 +7,7 @@ export const getU64Encoder = (config: NumberCodecConfig = {}): FixedSizeEncoder<
     numberEncoderFactory({
         config,
         name: 'u64',
-        range: [0, BigInt('0xffffffffffffffff')],
+        range: [0n, BigInt('0xffffffffffffffff')],
         set: (view, value, le) => view.setBigUint64(0, BigInt(value), le),
         size: 8,
     });