diff --git a/index.d.ts b/index.d.ts
index c276e4d..ecc0a2d 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -21,15 +21,15 @@ export class Buffer extends Uint8Array {
     readUInt16BE(offset?: number, noAssert?: boolean): number;
     readUInt32LE(offset?: number, noAssert?: boolean): number;
     readUInt32BE(offset?: number, noAssert?: boolean): number;
-    readBigUInt64LE(offset?: number): BigInt;
-    readBigUInt64BE(offset?: number): BigInt;
+    readBigUInt64LE(offset?: number): bigint;
+    readBigUInt64BE(offset?: number): bigint;
     readInt8(offset?: number, noAssert?: boolean): number;
     readInt16LE(offset?: number, noAssert?: boolean): number;
     readInt16BE(offset?: number, noAssert?: boolean): number;
     readInt32LE(offset?: number, noAssert?: boolean): number;
     readInt32BE(offset?: number, noAssert?: boolean): number;
-    readBigInt64LE(offset?: number): BigInt;
-    readBigInt64BE(offset?: number): BigInt;
+    readBigInt64LE(offset?: number): bigint;
+    readBigInt64BE(offset?: number): bigint;
     readFloatLE(offset?: number, noAssert?: boolean): number;
     readFloatBE(offset?: number, noAssert?: boolean): number;
     readDoubleLE(offset?: number, noAssert?: boolean): number;
@@ -43,15 +43,15 @@ export class Buffer extends Uint8Array {
     writeUInt16BE(value: number, offset?: number, noAssert?: boolean): number;
     writeUInt32LE(value: number, offset?: number, noAssert?: boolean): number;
     writeUInt32BE(value: number, offset?: number, noAssert?: boolean): number;
-    writeBigUInt64LE(value: BigInt, offset?: number): number;
-    writeBigUInt64BE(value: BigInt, offset?: number): number;
+    writeBigUInt64LE(value: bigint, offset?: number): number;
+    writeBigUInt64BE(value: bigint, offset?: number): number;
     writeInt8(value: number, offset?: number, noAssert?: boolean): number;
     writeInt16LE(value: number, offset?: number, noAssert?: boolean): number;
     writeInt16BE(value: number, offset?: number, noAssert?: boolean): number;
     writeInt32LE(value: number, offset?: number, noAssert?: boolean): number;
     writeInt32BE(value: number, offset?: number, noAssert?: boolean): number;
-    writeBigInt64LE(value: BigInt, offset?: number): number;
-    writeBigInt64BE(value: BigInt, offset?: number): number;
+    writeBigInt64LE(value: bigint, offset?: number): number;
+    writeBigInt64BE(value: bigint, offset?: number): number;
     writeFloatLE(value: number, offset?: number, noAssert?: boolean): number;
     writeFloatBE(value: number, offset?: number, noAssert?: boolean): number;
     writeDoubleLE(value: number, offset?: number, noAssert?: boolean): number;