diff --git a/source/index.ts b/source/index.ts
index 782a067..848af80 100644
--- a/source/index.ts
+++ b/source/index.ts
@@ -413,6 +413,10 @@ export function isDate(value: unknown): value is Date {
 }
 
 export function isDirectInstanceOf<T>(instance: unknown, class_: Class<T>): instance is T {
+	if (instance === undefined || instance === null) {
+		return false;
+	}
+
 	return Object.getPrototypeOf(instance) === class_.prototype;
 }
 
diff --git a/test/test.ts b/test/test.ts
index 8608a25..bbf7b57 100644
--- a/test/test.ts
+++ b/test/test.ts
@@ -986,6 +986,9 @@ test('is.directInstanceOf', t => {
 	t.throws(() => {
 		assert.directInstanceOf(errorSubclass, Error);
 	});
+
+	t.false(is.directInstanceOf(undefined, Error));
+	t.false(is.directInstanceOf(null, Error));
 });
 
 test('is.urlInstance', t => {