diff --git a/src/files.ts b/src/files.ts
index 0e804d4f2..c52f02f04 100644
--- a/src/files.ts
+++ b/src/files.ts
@@ -7,13 +7,8 @@ import {cwd} from "node:process";
 import {fileURLToPath} from "node:url";
 import {isEnoent} from "./error.js";
 
-export function toOsPath(path: string): string {
-  return path.split(sep).join(op.sep);
-}
-
-export function fromOsPath(path: string): string {
-  return path.split(op.sep).join(sep);
-}
+export const toOsPath = sep === op.sep ? (path: string) => path : (path: string) => path.split(sep).join(op.sep);
+export const fromOsPath = sep === op.sep ? (path: string) => path : (path: string) => path.split(op.sep).join(sep);
 
 /**
  * Returns the relative path from the current working directory to the given
diff --git a/src/path.ts b/src/path.ts
index 3e92766d4..5dc315336 100644
--- a/src/path.ts
+++ b/src/path.ts
@@ -1,4 +1,5 @@
-import {dirname, isAbsolute, join, normalize, relative, resolve} from "node:path/posix";
+import op from "node:path";
+import {dirname, join} from "node:path/posix";
 
 /**
  * Returns the normalized relative path from "/file/path/to/a" to
@@ -86,6 +87,7 @@ export function parseRelativeUrl(url: string): {pathname: string; search: string
 }
 
 export function within(root: string, path: string): boolean {
+  const {relative, normalize, resolve, isAbsolute} = op;
   path = relative(normalize(resolve(root)), normalize(resolve(path)));
   return !path.startsWith("..") && !isAbsolute(path);
 }
diff --git a/test/path-test.ts b/test/path-test.ts
index 9ac9a8c02..3e373c7fb 100644
--- a/test/path-test.ts
+++ b/test/path-test.ts
@@ -1,5 +1,5 @@
 import assert from "node:assert";
-import {isPathImport, parseRelativeUrl, relativePath, resolveLocalPath, resolvePath} from "../src/path.js";
+import {isPathImport, parseRelativeUrl, relativePath, resolveLocalPath, resolvePath, within} from "../src/path.js";
 
 describe("resolvePath(source, target)", () => {
   it("returns the path to the specified target within the source root", () => {
@@ -151,3 +151,21 @@ describe("parseRelativeUrl(url)", () => {
     assert.deepStrictEqual(parseRelativeUrl("foo?bar#baz"), {pathname: "foo", search: "?bar", hash: "#baz"});
   });
 });
+
+describe("within(root, path)", () => {
+  it("returns true for paths within the current working directory", () => {
+    assert.strictEqual(within(process.cwd(), "dist"), true, "dist");
+    assert.strictEqual(within(process.cwd(), "./dist"), true, "./dist");
+    assert.strictEqual(within(process.cwd(), "dist/"), true, "dist/");
+    assert.strictEqual(within(process.cwd(), "./dist/"), true, "./dist/");
+    assert.strictEqual(within(process.cwd(), "foo/../dist"), true, "foo/../dist");
+    assert.strictEqual(within(process.cwd(), "foo/../dist/"), true, "foo/../dist/");
+    assert.strictEqual(within(process.cwd(), "./foo/../dist/"), true, "./foo/../dist/");
+    assert.strictEqual(within(process.cwd(), "foo/bar"), true, "foo/bar");
+    assert.strictEqual(within(process.cwd(), "foo/bar"), true, "foo/bar");
+    assert.strictEqual(within(process.cwd(), "../framework/dist"), true, "../framework/dist");
+    assert.strictEqual(within(process.cwd(), "../framework2/dist"), false, "../framework2/dist");
+    assert.strictEqual(within(process.cwd(), "../dist"), false, "../dist");
+    assert.strictEqual(within(process.cwd(), "/dist"), false, "/dist");
+  });
+});