diff --git a/src/index.ts b/src/index.ts
index 585ae0e..1c43b92 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -7,7 +7,7 @@ export function isNumber(value: unknown): value is number {
 }
 
 export function isBigInt(value: unknown): value is bigint {
-  return typeof value === 'boolean';
+  return typeof value === 'bigint';
 }
 
 export function isBoolean(value: unknown): value is boolean {