diff --git a/README.md b/README.md
index 640d39b8..ef6d00c3 100644
--- a/README.md
+++ b/README.md
@@ -557,7 +557,15 @@ const options = {
     [/@endawait$/gim, '{/await}'],
     [/@debug\s*\((.*?)\)$/gim, '{@debug $1}'],
     [/@html\s*\((.*?)\)$/gim, '{@html $1}'],
-  ];
+  ],
+
+  /** Configure globalStyle and globalRule source map options */
+  globalStyle: {
+    sourceMap: true,
+  },
+  globalRule: {
+    sourceMap: true,
+  },
 };
 
 svelte.preprocess(input, sveltePreprocess(options));
diff --git a/src/autoProcess.ts b/src/autoProcess.ts
index 106fe6aa..531a7082 100644
--- a/src/autoProcess.ts
+++ b/src/autoProcess.ts
@@ -24,8 +24,8 @@ interface Transformers {
   postcss?: TransformerOptions<Options.Postcss>;
   coffeescript?: TransformerOptions<Options.Coffeescript>;
   pug?: TransformerOptions<Options.Pug>;
-  globalStyle?: TransformerOptions;
-  globalRule?: TransformerOptions;
+  globalStyle?: Options.GlobalStyle;
+  globalRule?: Options.GlobalRule;
   replace?: Options.Replace;
   [languageName: string]: TransformerOptions;
 }
@@ -53,8 +53,8 @@ type AutoPreprocessOptions = {
   babel?: TransformerOptions<Options.Babel>;
   coffeescript?: TransformerOptions<Options.Coffeescript>;
   pug?: TransformerOptions<Options.Pug>;
-  globalStyle?: TransformerOptions<Options.Typescript>;
-  globalRule?: TransformerOptions<Options.Typescript>;
+  globalStyle?: Options.GlobalStyle;
+  globalRule?: Options.GlobalRule;
   // workaround while we don't have this
   // https://github.com/microsoft/TypeScript/issues/17867
   [languageName: string]:
@@ -263,21 +263,29 @@ export function autoPreprocess(
 
       if (await hasPostCssInstalled()) {
         if (attributes.global) {
-          const transformed = await runTransformer('globalStyle', null, {
-            content: code,
-            map,
-            filename,
-          });
+          const transformed = await runTransformer(
+            'globalStyle',
+            transformers?.globalStyle,
+            {
+              content: code,
+              map,
+              filename,
+            },
+          );
 
           code = transformed.code;
           map = transformed.map;
         }
 
-        const transformed = await runTransformer('globalRule', null, {
-          content: code,
-          map,
-          filename,
-        });
+        const transformed = await runTransformer(
+          'globalRule',
+          transformers?.globalRule,
+          {
+            content: code,
+            map,
+            filename,
+          },
+        );
 
         code = transformed.code;
         map = transformed.map;
diff --git a/src/transformers/globalRule.ts b/src/transformers/globalRule.ts
index 65872d2d..a3010963 100644
--- a/src/transformers/globalRule.ts
+++ b/src/transformers/globalRule.ts
@@ -1,25 +1,43 @@
 import postcss from 'postcss';
 
-import { Transformer } from '../types';
+import { Transformer, Options } from '../types';
 import { globalifySelector } from '../modules/globalifySelector';
 
 const selectorPattern = /:global(?!\()/;
 
-const globalifyRulePlugin = (root: any) => {
-  root.walkRules(selectorPattern, (rule: any) => {
-    const [beginning, ...rest] = rule.selector.split(selectorPattern);
+const globalifyRulePlugin: postcss.Transformer = (root) => {
+  root.walkRules(selectorPattern, (rule) => {
+    const modifiedSelectors = rule.selectors.map((selector) => {
+      const [beginning, ...rest] = selector.split(selectorPattern);
 
-    rule.selector = [beginning, ...rest.map(globalifySelector)]
-      .map((str) => str.trim())
-      .join(' ')
-      .trim();
+      if (rest.length === 0) return;
+
+      return [beginning, ...rest.map(globalifySelector)]
+        .map((str) => str.trim())
+        .join(' ')
+        .trim();
+    });
+
+    rule.replaceWith(
+      rule.clone({
+        selectors: modifiedSelectors,
+      }),
+    );
   });
 };
 
-const transformer: Transformer<never> = async ({ content, filename }) => {
+// todo - this can be merged with the globalStyle
+const transformer: Transformer<Options.GlobalRule> = async ({
+  content,
+  filename,
+  options,
+}) => {
   const { css, map: newMap } = await postcss()
     .use(globalifyRulePlugin)
-    .process(content, { from: filename, map: false });
+    .process(content, {
+      from: filename,
+      map: options?.sourceMap ?? false,
+    });
 
   return { code: css, map: newMap };
 };
diff --git a/src/transformers/globalStyle.ts b/src/transformers/globalStyle.ts
index 547eff1a..e19215ed 100644
--- a/src/transformers/globalStyle.ts
+++ b/src/transformers/globalStyle.ts
@@ -1,28 +1,43 @@
-import postcss from 'postcss';
+import postcss, { AtRule } from 'postcss';
 
-import { Transformer } from '../types';
+import { Transformer, Options } from '../types';
 import { globalifySelector } from '../modules/globalifySelector';
 
-const globalifyPlugin = (root: any) => {
-  root.walkAtRules(/keyframes$/, (atrule: any) => {
+const globalifyPlugin = (root: postcss.Root) => {
+  root.walkAtRules(/keyframes$/, (atrule) => {
     if (!atrule.params.startsWith('-global-')) {
-      atrule.params = `-global-${atrule.params}`;
+      atrule.replaceWith(
+        atrule.clone({
+          params: `-global-${atrule.params}`,
+        }),
+      );
     }
   });
 
-  root.walkRules((rule: any) => {
-    if (rule.parent && rule.parent.name === 'keyframes') {
+  root.walkRules((rule) => {
+    if ((rule?.parent as AtRule)?.name === 'keyframes') {
       return;
     }
 
-    rule.selectors = rule.selectors.map(globalifySelector);
+    rule.replaceWith(
+      rule.clone({
+        selectors: rule.selectors.map(globalifySelector),
+      }),
+    );
   });
 };
 
-const transformer: Transformer<never> = async ({ content, filename }) => {
+const transformer: Transformer<Options.GlobalStyle> = async ({
+  content,
+  filename,
+  options,
+}) => {
   const { css, map: newMap } = await postcss()
     .use(globalifyPlugin)
-    .process(content, { from: filename, map: false });
+    .process(content, {
+      from: filename,
+      map: options?.sourceMap ?? false,
+    });
 
   return { code: css, map: newMap };
 };
diff --git a/src/types/index.ts b/src/types/index.ts
index 265441c2..501e4052 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -35,5 +35,5 @@ export type Transformer<T> = (
 
 export type TransformerOptions<T = any> =
   | boolean
-  | Record<string, any>
+  | Record<keyof T | string, T[keyof T] | any>
   | Transformer<T>;
diff --git a/src/types/options.ts b/src/types/options.ts
index 17a98d98..7a822dd6 100644
--- a/src/types/options.ts
+++ b/src/types/options.ts
@@ -67,3 +67,11 @@ export interface Typescript {
   transpileOnly?: boolean;
   reportDiagnostics?: boolean;
 }
+
+export interface GlobalRule {
+  sourceMap: boolean;
+}
+
+export interface GlobalStyle {
+  sourceMap: boolean;
+}
diff --git a/test/transformers/globalRule.test.ts b/test/transformers/globalRule.test.ts
index df8d08d6..9b76a5e8 100644
--- a/test/transformers/globalRule.test.ts
+++ b/test/transformers/globalRule.test.ts
@@ -9,6 +9,18 @@ describe('transformer - globalRule', () => {
     expect(() => preprocess(template, opts)).not.toThrow();
   });
 
+  it('adds sourceMap with { sourceMap: true }', async () => {
+    const template = `<style>:global div{color:red}:global .test{}</style>`;
+    const opts = autoProcess({
+      globalRule: {
+        sourceMap: true,
+      },
+    });
+    const preprocessed = await preprocess(template, opts);
+
+    expect(preprocessed.toString()).toContain(`sourceMappingURL`);
+  });
+
   it('wraps selector in :global(...) modifier', async () => {
     const template = `<style>:global div{color:red}:global .test{}</style>`;
     const opts = autoProcess();
diff --git a/test/transformers/globalStyle.test.ts b/test/transformers/globalStyle.test.ts
index 3e32caac..946d8794 100644
--- a/test/transformers/globalStyle.test.ts
+++ b/test/transformers/globalStyle.test.ts
@@ -2,6 +2,19 @@ import autoProcess from '../../src';
 import { preprocess } from '../utils';
 
 describe('transformer - globalStyle', () => {
+  // todo: why it isn't generating a sourcemap?
+  it.skip('adds sourceMap with { sourceMap: true }', async () => {
+    const template = `<style global>div,span{color:red}.test{}</style>`;
+    const opts = autoProcess({
+      globalStyle: {
+        sourceMap: true,
+      },
+    });
+    const preprocessed = await preprocess(template, opts);
+
+    expect(preprocessed.toString()).toContain(`sourceMappingURL`);
+  });
+
   it('wraps selector in :global(...) modifier', async () => {
     const template = `<style global>div{color:red}.test{}</style>`;
     const opts = autoProcess();