diff --git a/src/internal/utils/isTraverser.ts b/src/internal/utils/isTraverser.ts
index 2e431a9..ad4e115 100644
--- a/src/internal/utils/isTraverser.ts
+++ b/src/internal/utils/isTraverser.ts
@@ -1,9 +1,10 @@
 import type { Traverser } from '../../api';
 
-export function isTraverser<D>(candidate: Traverser<D> | unknown): candidate is Traverser<D> {
+export function isTraverser<D>(candidate: unknown): candidate is Traverser<D> {
   const t = candidate as Traverser<D>;
   return (
     !!t &&
+    typeof t === 'object' &&
     t.traversable !== null &&
     typeof t.traversable === 'object' &&
     t.traversalConfig !== null &&