diff --git a/packages/utils/src/eslint-utils/deepMerge.ts b/packages/utils/src/eslint-utils/deepMerge.ts
index 9d275ecfc61..85412ed399d 100644
--- a/packages/utils/src/eslint-utils/deepMerge.ts
+++ b/packages/utils/src/eslint-utils/deepMerge.ts
@@ -6,7 +6,7 @@ type ObjectLike<T = unknown> = Record<string, T>;
  * @returns `true` if obj is an object
  */
 function isObjectNotArray<T extends ObjectLike>(obj: unknown): obj is T {
-  return typeof obj === 'object' && !Array.isArray(obj);
+  return typeof obj === 'object' && obj != null && !Array.isArray(obj);
 }
 
 /**
diff --git a/packages/utils/tests/eslint-utils/applyDefault.test.ts b/packages/utils/tests/eslint-utils/applyDefault.test.ts
index ec9411c31c2..12566d44e94 100644
--- a/packages/utils/tests/eslint-utils/applyDefault.test.ts
+++ b/packages/utils/tests/eslint-utils/applyDefault.test.ts
@@ -59,4 +59,18 @@ describe('applyDefault', () => {
     expect(result).not.toBe(defaults);
     expect(result).not.toBe(user);
   });
+
+  it('should work when default option is null', () => {
+    const defaults: unknown[] = [null];
+    const user: unknown[] = [
+      {
+        prop: 'setting1',
+        other: 'other',
+      },
+    ];
+    const result = ESLintUtils.applyDefault(defaults, user);
+    expect(result).toStrictEqual(user);
+    expect(result).not.toBe(defaults);
+    expect(result).not.toBe(user);
+  });
 });