diff --git a/src/autoProcess.ts b/src/autoProcess.ts
index d846fe0e..4db85095 100644
--- a/src/autoProcess.ts
+++ b/src/autoProcess.ts
@@ -22,6 +22,12 @@ import type {
   Transformers,
 } from './types';
 
+const TARGET_LANGUAGES = Object.freeze({
+  markup: 'html',
+  style: 'css',
+  script: 'javascript',
+});
+
 export const transform = async (
   name: string | null | undefined,
   options: TransformerOptions,
@@ -53,25 +59,10 @@ export function sveltePreprocess(
     aliases,
     markupTagName = 'template',
     preserve = [],
-    defaults,
     sourceMap = process?.env?.NODE_ENV === 'development' ?? false,
     ...rest
   } = {} as AutoPreprocessOptions,
 ): AutoPreprocessGroup {
-  const defaultLanguages = Object.freeze({
-    markup: 'html',
-    style: 'css',
-    script: 'javascript',
-    ...defaults,
-  });
-
-  // todo: remove this on v5
-  if (defaults != null) {
-    console.warn(
-      '[svelte-preprocess] Deprecation notice: using the "defaults" option is no longer recommended and will be removed in the next major version. Instead, define the language being used explicitly via the lang attribute.\n\nSee https://github.com/sveltejs/svelte-preprocess/issues/362',
-    );
-  }
-
   const transformers = rest as Transformers;
 
   if (aliases?.length) {
@@ -133,7 +124,7 @@ export function sveltePreprocess(
         await getTagInfo(svelteFile);
 
       if (lang == null || alias == null) {
-        alias = defaultLanguages[type];
+        alias = TARGET_LANGUAGES[type];
         lang = getLanguageFromAlias(alias);
       }
 
@@ -284,7 +275,6 @@ export function sveltePreprocess(
   };
 
   return {
-    defaultLanguages,
     markup,
     script,
     style,
diff --git a/src/types/index.ts b/src/types/index.ts
index cb1811a2..d7b19a68 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -63,24 +63,12 @@ export interface Transformers {
   [language: string]: TransformerOptions;
 }
 
-export type AutoPreprocessGroup = PreprocessorGroup & {
-  defaultLanguages: Readonly<{
-    markup: string;
-    style: string;
-    script: string;
-  }>;
-};
+export type AutoPreprocessGroup = PreprocessorGroup;
 
 export type AutoPreprocessOptions = {
   markupTagName?: string;
   aliases?: Array<[string, string]>;
   preserve?: string[];
-  /** @deprecated Don't use "defaults" anymore, define the language being used explicitly instead */
-  defaults?: {
-    markup?: string;
-    style?: string;
-    script?: string;
-  };
   sourceMap?: boolean;
 
   // transformers
diff --git a/test/autoProcess/autoProcess.test.ts b/test/autoProcess/autoProcess.test.ts
index 07086e6e..c13afc9a 100644
--- a/test/autoProcess/autoProcess.test.ts
+++ b/test/autoProcess/autoProcess.test.ts
@@ -137,34 +137,6 @@ describe('options', () => {
     expect(await doesCompileThrow(input, opts)).toBe(true);
   });
 
-  it('should accept other languages as default', async () => {
-    const input = `<template>markup</template><style>style</style><script>script</script>`;
-
-    const opts = sveltePreprocess({
-      defaults: {
-        markup: 'customMarkup',
-        script: 'customScript',
-        style: 'customStyle',
-      },
-      globalStyle: false,
-      customMarkup({ content }: any) {
-        return { code: content.replace('markup', 'potato') };
-      },
-      customScript({ content }: any) {
-        return { code: content.replace('script', 'potato') };
-      },
-      customStyle({ content }: any) {
-        return { code: content.replace('style', 'potato') };
-      },
-    });
-
-    const preprocessed = await preprocess(input, opts);
-
-    expect(preprocessed.toString?.()).toContain(
-      'potato<style>potato</style><script>potato</script>',
-    );
-  });
-
   it('should respect lang/type attributes even if another default language is set', async () => {
     const input = `<script lang="tomatoScript">script</script>`;
 
@@ -186,21 +158,4 @@ describe('options', () => {
       '<script lang="tomatoScript">tomato</script>',
     );
   });
-
-  it('should be able to use default markup language with template tags', async () => {
-    const input = `potato`;
-
-    const opts = sveltePreprocess({
-      defaults: {
-        markup: 'potatoScript',
-      },
-      potatoScript({ content }: any) {
-        return { code: content.replace('potato', 'french-fries') };
-      },
-    });
-
-    const preprocessed = await preprocess(input, opts);
-
-    expect(preprocessed.toString?.()).toContain('french-fries');
-  });
 });