diff --git a/src/helpers.ts b/src/helpers.ts
index 21f3742..1f659b7 100644
--- a/src/helpers.ts
+++ b/src/helpers.ts
@@ -1,3 +1,4 @@
+import { FilterPattern, normalizePath } from "@rollup/pluginutils";
 import path from "path";
 import { OutputOptions } from "rollup";
 
@@ -24,3 +25,16 @@ export function getRelativeImportPath(from: string, to: string) {
 
 	return import_path;
 }
+
+export function normalizeFilterPattern(pattern?: FilterPattern): FilterPattern | undefined {
+	if (typeof pattern === "string") return normalizePath(pattern);
+
+	if (Array.isArray(pattern)) {
+		return pattern.map(element => {
+			if (typeof element === "string") return normalizePath(element);
+			return element;
+		});
+	}
+
+	return pattern;
+}
diff --git a/src/index.ts b/src/index.ts
index 3a8a48f..4a3c6b3 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -3,7 +3,7 @@ import path from "path";
 import { Plugin } from "rollup";
 import { createFilter, FilterPattern } from "@rollup/pluginutils";
 import { parse, print, types, visit } from "recast";
-import { getOutputId, getRelativeImportPath } from "./helpers";
+import { getOutputId, getRelativeImportPath, normalizeFilterPattern } from "./helpers";
 
 const PLUGIN_NAME = "external-assets";
 const PREFIX = `\0${PLUGIN_NAME}:`;
@@ -34,6 +34,8 @@ export default function externalAssets(
 	exclude?: FilterPattern,
 	options?: Options,
 ): Plugin {
+	include = normalizeFilterPattern(include);
+	exclude = normalizeFilterPattern(exclude);
 	const idFilter = createFilter(include, exclude, options);
 	const assets = new Map<string, Buffer>();
 
diff --git a/tests/unit.test.ts b/tests/unit.test.ts
index 85a3313..9e91f5f 100644
--- a/tests/unit.test.ts
+++ b/tests/unit.test.ts
@@ -1,5 +1,5 @@
 import path from "path";
-import { getOutputId } from "../src/helpers";
+import { getOutputId, normalizeFilterPattern } from "../src/helpers";
 
 test("getOutputId", () => {
 	expect(getOutputId("a.ext", { dir: "out" })).toBe(path.resolve("out/a.ext"));
@@ -12,3 +12,23 @@ test("getOutputId", () => {
 	expect(getOutputId("a.ext", {})).toBe(path.resolve("a.ext"));
 	expect(getOutputId("a/b.ext", {})).toBe(path.resolve("a/b.ext"));
 });
+
+test("normalizeFilterPattern", () => {
+	expect(normalizeFilterPattern()).toBeUndefined();
+	expect(normalizeFilterPattern(null)).toBeNull();
+	expect(normalizeFilterPattern(/\.txt/g)).toStrictEqual(/\.txt/g);
+	expect(normalizeFilterPattern("abc/def/**/*")).toBe("abc/def/**/*");
+	expect(normalizeFilterPattern("abc\\def\\**\\*")).toBe("abc/def/**/*");
+	expect(normalizeFilterPattern(path.resolve("abc/def/**/*"))).toBe(path.resolve("abc/def/**/*").replace(/\\/g, "/"));
+	expect([
+		normalizeFilterPattern(/\.txt/g),
+		normalizeFilterPattern("abc/def/**/*"),
+		normalizeFilterPattern("abc\\def\\**\\*"),
+		normalizeFilterPattern(path.resolve("abc/def/**/*")),
+	]).toStrictEqual([
+		/\.txt/g,
+		"abc/def/**/*",
+		"abc/def/**/*",
+		path.resolve("abc/def/**/*").replace(/\\/g, "/"),
+	]);
+});