diff --git a/src/index.ts b/src/index.ts
index eb6920c5..e3f412d5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -7,13 +7,15 @@ import { ReaderAsync, ReaderStream, ReaderSync } from './readers';
 import type { Options as OptionsInternal } from './settings';
 import type { Entry as EntryInternal, EntryItem, FileSystemAdapter as FileSystemAdapterInternal, Pattern as PatternInternal } from './types';
 
+type InputPattern = PatternInternal | readonly PatternInternal[];
+
 type EntryObjectModePredicate = { [TKey in keyof Pick<OptionsInternal, 'objectMode'>]-?: true };
 type EntryStatsPredicate = { [TKey in keyof Pick<OptionsInternal, 'stats'>]-?: true };
 type EntryObjectPredicate = EntryObjectModePredicate | EntryStatsPredicate;
 
-function FastGlob(source: PatternInternal | PatternInternal[], options: EntryObjectPredicate & OptionsInternal): Promise<EntryInternal[]>;
-function FastGlob(source: PatternInternal | PatternInternal[], options?: OptionsInternal): Promise<string[]>;
-async function FastGlob(source: PatternInternal | PatternInternal[], options?: OptionsInternal): Promise<EntryItem[]> {
+function FastGlob(source: InputPattern, options: EntryObjectPredicate & OptionsInternal): Promise<EntryInternal[]>;
+function FastGlob(source: InputPattern, options?: OptionsInternal): Promise<string[]>;
+async function FastGlob(source: InputPattern, options?: OptionsInternal): Promise<EntryItem[]> {
 	assertPatternsInput(source);
 
 	const settings = new Settings(options);
@@ -41,9 +43,9 @@ namespace FastGlob {
 
 	export const async = FastGlob;
 
-	export function sync(source: PatternInternal | PatternInternal[], options: EntryObjectPredicate & OptionsInternal): EntryInternal[];
-	export function sync(source: PatternInternal | PatternInternal[], options?: OptionsInternal): string[];
-	export function sync(source: PatternInternal | PatternInternal[], options?: OptionsInternal): EntryItem[] {
+	export function sync(source: InputPattern, options: EntryObjectPredicate & OptionsInternal): EntryInternal[];
+	export function sync(source: InputPattern, options?: OptionsInternal): string[];
+	export function sync(source: InputPattern, options?: OptionsInternal): EntryItem[] {
 		assertPatternsInput(source);
 
 		const settings = new Settings(options);
@@ -56,7 +58,7 @@ namespace FastGlob {
 		return utils.array.flatFirstLevel(entries);
 	}
 
-	export function stream(source: PatternInternal | PatternInternal[], options?: OptionsInternal): NodeJS.ReadableStream {
+	export function stream(source: InputPattern, options?: OptionsInternal): NodeJS.ReadableStream {
 		assertPatternsInput(source);
 
 		const settings = new Settings(options);
@@ -74,7 +76,7 @@ namespace FastGlob {
 		return utils.stream.merge(streams);
 	}
 
-	export function generateTasks(source: PatternInternal | PatternInternal[], options?: OptionsInternal): Task[] {
+	export function generateTasks(source: InputPattern, options?: OptionsInternal): Task[] {
 		assertPatternsInput(source);
 
 		const patterns = ([] as PatternInternal[]).concat(source);
@@ -132,7 +134,7 @@ namespace FastGlob {
 	}
 }
 
-function getTasks(source: PatternInternal | PatternInternal[], settings: Settings): taskManager.Task[] {
+function getTasks(source: InputPattern, settings: Settings): taskManager.Task[] {
 	const patterns = ([] as PatternInternal[]).concat(source);
 
 	return taskManager.generate(patterns, settings);
diff --git a/src/managers/tasks.ts b/src/managers/tasks.ts
index f0b1a9b9..dab09743 100644
--- a/src/managers/tasks.ts
+++ b/src/managers/tasks.ts
@@ -11,9 +11,9 @@ export interface Task {
 	negative: Pattern[];
 }
 
-export function generate(input: Pattern[], settings: Settings): Task[] {
-	const patterns = processPatterns(input, settings);
-	const ignore = processPatterns(settings.ignore, settings);
+export function generate(input: readonly Pattern[], settings: Settings): Task[] {
+	const patterns = processPatterns([...input], settings);
+	const ignore = processPatterns([...settings.ignore], settings);
 
 	const positivePatterns = getPositivePatterns(patterns);
 	const negativePatterns = getNegativePatternsAsPositive(patterns, ignore);
diff --git a/src/settings.ts b/src/settings.ts
index 8900b04e..d16e7757 100644
--- a/src/settings.ts
+++ b/src/settings.ts
@@ -95,7 +95,7 @@ export interface Options {
 	 *
 	 * @default []
 	 */
-	ignore?: Pattern[];
+	ignore?: readonly Pattern[];
 	/**
 	 * Mark the directory path with the final slash.
 	 *
@@ -161,7 +161,7 @@ export default class Settings {
 	public readonly followSymbolicLinks: boolean;
 	public readonly fs: FileSystemAdapter;
 	public readonly globstar: boolean;
-	public readonly ignore: Pattern[];
+	public readonly ignore: readonly Pattern[];
 	public readonly markDirectories: boolean;
 	public readonly objectMode: boolean;
 	public readonly onlyDirectories: boolean;