diff --git a/packages/app-cli/tests/services_PluginService.ts b/packages/app-cli/tests/services_PluginService.ts
index 4f0a21ed1..33d210fec 100644
--- a/packages/app-cli/tests/services_PluginService.ts
+++ b/packages/app-cli/tests/services_PluginService.ts
@@ -170,7 +170,9 @@ describe('services_PluginService', function() {
 		const tempDir = await createTempDir();
 
 		const contentScriptPath = `${tempDir}/markdownItTestPlugin.js`;
+		const contentScriptCssPath = `${tempDir}/markdownItTestPlugin.css`;
 		await shim.fsDriver().copy(`${testPluginDir}/content_script/src/markdownItTestPlugin.js`, contentScriptPath);
+		await shim.fsDriver().copy(`${testPluginDir}/content_script/src/markdownItTestPlugin.css`, contentScriptCssPath);
 
 		const service = newPluginService();
 
@@ -205,7 +207,7 @@ describe('services_PluginService', function() {
 
 		const mdToHtml = new MdToHtml();
 		const module = require(contentScript.path).default;
-		mdToHtml.loadExtraRendererRule(contentScript.id, module({}));
+		mdToHtml.loadExtraRendererRule(contentScript.id, tempDir, module({}));
 
 		const result = await mdToHtml.render([
 			'```justtesting',
@@ -213,6 +215,11 @@ describe('services_PluginService', function() {
 			'```',
 		].join('\n'));
 
+		const asset = result.pluginAssets.find(a => a.name === 'justtesting/markdownItTestPlugin.css');
+		const assetContent: string = await shim.fsDriver().readFile(asset.path, 'utf8');
+
+		expect(assetContent.includes('.just-testing')).toBe(true);
+		expect(assetContent.includes('background-color: red;')).toBe(true);
 		expect(result.html.includes('JUST TESTING: something')).toBe(true);
 
 		await shim.fsDriver().remove(tempDir);
diff --git a/packages/app-cli/tests/support/plugins/content_script/package.json b/packages/app-cli/tests/support/plugins/content_script/package.json
index a7ad2623f..761cec9f9 100644
--- a/packages/app-cli/tests/support/plugins/content_script/package.json
+++ b/packages/app-cli/tests/support/plugins/content_script/package.json
@@ -20,4 +20,4 @@
     "webpack": "^4.43.0",
     "webpack-cli": "^3.3.11"
   }
-}
\ No newline at end of file
+}
diff --git a/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.css b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.css
new file mode 100644
index 000000000..a168fce07
--- /dev/null
+++ b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.css
@@ -0,0 +1,4 @@
+.just-testing {
+	background-color: red;
+	color: yellow;
+}
\ No newline at end of file
diff --git a/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.js b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.js
index bc6bc2aac..a294bfb25 100644
--- a/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.js
+++ b/packages/app-cli/tests/support/plugins/content_script/src/markdownItTestPlugin.js
@@ -6,7 +6,7 @@ function plugin(markdownIt, _options) {
 	markdownIt.renderer.rules.fence = function(tokens, idx, options, env, self) {
 		const token = tokens[idx];
 		if (token.info !== 'justtesting') return defaultRender(tokens, idx, options, env, self);
-		return `JUST TESTING: ${token.content}`;
+		return `<div class="just-testing">JUST TESTING: ${token.content}</div>`;
 	};
 }
 
@@ -14,6 +14,11 @@ module.exports = {
 	default: function(_context) { 
 		return {
 			plugin: plugin,
+			assets: function() {
+				return [
+					{ name: 'markdownItTestPlugin.css' }
+				];
+			},
 		}
 	},
 }
diff --git a/packages/renderer/MdToHtml.ts b/packages/renderer/MdToHtml.ts
index 1b71b3577..f257105f6 100644
--- a/packages/renderer/MdToHtml.ts
+++ b/packages/renderer/MdToHtml.ts
@@ -9,6 +9,7 @@ interface RendererRule {
 	install(context: any, ruleOptions: any): any;
 	assets?(theme: any): any;
 	plugin?: any;
+	assetPath?: string;
 }
 
 interface RendererRules {
@@ -197,7 +198,7 @@ export default class MdToHtml {
 
 		if (options.extraRendererRules) {
 			for (const rule of options.extraRendererRules) {
-				this.loadExtraRendererRule(rule.id, rule.module);
+				this.loadExtraRendererRule(rule.id, rule.assetPath, rule.module);
 			}
 		}
 	}
@@ -232,15 +233,28 @@ export default class MdToHtml {
 	}
 
 	// `module` is a file that has already been `required()`
-	public loadExtraRendererRule(id: string, module: any) {
+	public loadExtraRendererRule(id: string, assetPath: string, module: any) {
 		if (this.extraRendererRules_[id]) throw new Error(`A renderer rule with this ID has already been loaded: ${id}`);
-		this.extraRendererRules_[id] = module;
+		this.extraRendererRules_[id] = {
+			...module,
+			assetPath,
+		};
+	}
+
+	private ruleByKey(key: string): RendererRule {
+		if (rules[key]) return rules[key];
+		if (this.extraRendererRules_[key]) return this.extraRendererRules_[key];
+		if (key === 'highlight.js') return null;
+		throw new Error(`No such rule: ${key}`);
 	}
 
 	private processPluginAssets(pluginAssets: PluginAssets): RenderResult {
 		const files: RenderResultPluginAsset[] = [];
 		const cssStrings = [];
 		for (const pluginName in pluginAssets) {
+
+			const rule = this.ruleByKey(pluginName);
+
 			for (const asset of pluginAssets[pluginName]) {
 				let mime = asset.mime;
 
@@ -263,10 +277,18 @@ export default class MdToHtml {
 						throw new Error(`Unsupported inline mime type: ${mime}`);
 					}
 				} else {
+					// TODO: we should resolve the path using
+					// resolveRelativePathWithinDir() for increased
+					// security, but the shim is not accessible from the
+					// renderer, and React Native doesn't have this
+					// function, so for now use the provided path as-is.
+
 					const name = `${pluginName}/${asset.name}`;
+					const assetPath = rule?.assetPath ? `${rule.assetPath}/${asset.name}` : `pluginAssets/${name}`;
+
 					files.push(Object.assign({}, asset, {
 						name: name,
-						path: `pluginAssets/${name}`,
+						path: assetPath,
 						mime: mime,
 					}));
 				}
@@ -282,7 +304,7 @@ export default class MdToHtml {
 
 	// This return all the assets for all the plugins. Since it is called
 	// on each render, the result is cached.
-	private allProcessedAssets(theme: any, codeTheme: string) {
+	private allProcessedAssets(rules: RendererRules, theme: any, codeTheme: string) {
 		const cacheKey: string = theme.cacheKey + codeTheme;
 
 		if (this.allProcessedAssets_[cacheKey]) return this.allProcessedAssets_[cacheKey];
@@ -501,7 +523,7 @@ export default class MdToHtml {
 
 		let cssStrings = noteStyle(options.theme);
 
-		let output = { ...this.allProcessedAssets(options.theme, options.codeTheme) };
+		let output = { ...this.allProcessedAssets(allRules, options.theme, options.codeTheme) };
 		cssStrings = cssStrings.concat(output.cssStrings);
 
 		if (options.userCss) cssStrings.push(options.userCss);