diff --git a/postcss-selector-parser.d.ts b/postcss-selector-parser.d.ts
index 9f0a233..0625005 100644
--- a/postcss-selector-parser.d.ts
+++ b/postcss-selector-parser.d.ts
@@ -18,12 +18,12 @@ export = parser;
 type Diff<T, U> = T extends U ? never : T;
 
 // TODO: Conditional types in TS 1.8 will really clean this up.
-declare function parser(): parser.Processor<never>;
-declare function parser<Transform>(processor: parser.AsyncProcessor<Transform>): parser.Processor<Transform, never>;
-declare function parser(processor: parser.AsyncProcessor<void>): parser.Processor<never, never>;
-declare function parser<Transform>(processor: parser.SyncProcessor<Transform>): parser.Processor<Transform>;
-declare function parser(processor: parser.SyncProcessor<void>): parser.Processor<never>;
-declare function parser<Transform>(processor?: parser.SyncProcessor<Transform> | parser.AsyncProcessor<Transform>): parser.Processor<Transform>;
+declare function parser(processor?: undefined, options?: Partial<parser.Options>): parser.Processor<never>;
+declare function parser<Transform>(processor: parser.AsyncProcessor<Transform>, options?: Partial<parser.Options>): parser.Processor<Transform, never>;
+declare function parser(processor: parser.AsyncProcessor<void>, options?: Partial<parser.Options>): parser.Processor<never, never>;
+declare function parser<Transform>(processor: parser.SyncProcessor<Transform>, options?: Partial<parser.Options>): parser.Processor<Transform>;
+declare function parser(processor: parser.SyncProcessor<void>, options?: Partial<parser.Options>): parser.Processor<never>;
+declare function parser<Transform>(processor?: parser.SyncProcessor<Transform> | parser.AsyncProcessor<Transform>, options?: Partial<parser.Options>): parser.Processor<Transform>;
 
 /*~ If you want to expose types from your module as well, you can
  *~ place them in this block. Often you will want to describe the
diff --git a/postcss-selector-parser.test.ts b/postcss-selector-parser.test.ts
index 5ba3fa7..e2d1fb7 100644
--- a/postcss-selector-parser.test.ts
+++ b/postcss-selector-parser.test.ts
@@ -1,5 +1,15 @@
 import * as parser from './postcss-selector-parser';
 
+parser(undefined, { lossless: false }).processSync('a > b');
+parser(() => {}, { lossless: false }).processSync('a > b');
+parser(() => 1, { lossless: false }).transformSync('a > b') satisfies number;
+declare const asyncProcessor: parser.AsyncProcessor<number>;
+declare const asyncVoidProcessor: parser.AsyncProcessor<void>;
+parser(asyncVoidProcessor, { lossless: false }).process('a > b');
+parser(asyncProcessor, { lossless: false }).transform('a > b') satisfies Promise<number>;
+// @ts-expect-error An async processor cannot be called synchronously.
+parser(asyncProcessor, { lossless: false }).processSync('a > b');
+
 parser((root) => {
     root.each((node, index) => {
         node satisfies parser.Selector;
diff --git a/src/__tests__/parser.mjs b/src/__tests__/parser.mjs
index cc5ccc0..48e65a1 100644
--- a/src/__tests__/parser.mjs
+++ b/src/__tests__/parser.mjs
@@ -49,6 +49,42 @@ test("no operation", (t) => {
   t.notThrows(() => parser().processSync("h1 h2 h3"));
 });
 
+test("default options work sync and can be overridden", (t) => {
+  const processor = parser(undefined, { lossless: false });
+  t.is(processor.processSync("a > b"), "a>b");
+  t.is(processor.processSync("a > b", { lossless: true }), "a > b");
+  t.is(processor.processSync("a > b"), "a>b");
+});
+
+test("default options work async and can be overridden", async (t) => {
+  const processor = parser(undefined, { lossless: false });
+  t.is(await processor.process("a > b"), "a>b");
+  t.is(await processor.process("a > b", { lossless: true }), "a > b");
+  t.is(await processor.process("a > b"), "a>b");
+});
+
+test("default maxNestingDepth works and can be overridden", (t) => {
+  const processor = parser(undefined, { maxNestingDepth: 1 });
+  const selector = ":not(:not(a))";
+  t.throws(() => processor.processSync(selector), { instanceOf: Error });
+  t.is(processor.processSync(selector, { maxNestingDepth: 10 }), selector);
+});
+
+test("default updateSelector works async and can be overridden", async (t) => {
+  const processor = parser(
+    (root) =>
+      root.walkClasses((node) => {
+        node.value = "bar";
+      }),
+    { updateSelector: false },
+  );
+  const rule = { selector: ".foo" };
+  t.is(await processor.process(rule), ".bar");
+  t.is(rule.selector, ".foo");
+  t.is(await processor.process(rule, { updateSelector: true }), ".bar");
+  t.is(rule.selector, ".bar");
+});
+
 test("empty selector string", (t) => {
   t.notThrows(() => {
     return parser((selectors) => {
diff --git a/src/index.ts b/src/index.ts
index 0d34e3f..e5889a6 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,7 @@
 import Processor from "./processor";
 import * as selectors from "./selectors";
 
-const parser = (processor?: any) => new Processor(processor);
+const parser = (processor?: any, options?: any) => new Processor(processor, options);
 
 Object.assign(parser, selectors);