diff --git a/extensions/css-language-features/client/src/cssMain.ts b/extensions/css-language-features/client/src/cssMain.ts
index 7520e61b209..ee8c9973d3a 100644
--- a/extensions/css-language-features/client/src/cssMain.ts
+++ b/extensions/css-language-features/client/src/cssMain.ts
@@ -11,7 +11,7 @@ const localize = nls.loadMessageBundle();
 
 import { languages, window, commands, ExtensionContext, Range, Position, CompletionItem, CompletionItemKind, TextEdit, SnippetString, workspace } from 'vscode';
 import { LanguageClient, LanguageClientOptions, ServerOptions, TransportKind, Disposable } from 'vscode-languageclient';
-import { getCustomDataPathsInAllWorkspaces } from './customData';
+import { getCustomDataPathsInAllWorkspaces, getCustomDataPathsFromAllExtensions } from './customData';
 
 // this method is called when vs code is activated
 export function activate(context: ExtensionContext) {
@@ -31,7 +31,10 @@ export function activate(context: ExtensionContext) {
 
 	let documentSelector = ['css', 'scss', 'less'];
 
-	let dataPaths = getCustomDataPathsInAllWorkspaces(workspace.workspaceFolders);
+	let dataPaths = [
+		...getCustomDataPathsInAllWorkspaces(workspace.workspaceFolders),
+		...getCustomDataPathsFromAllExtensions()
+	];
 
 	// Options to control the language client
 	let clientOptions: LanguageClientOptions = {
diff --git a/extensions/css-language-features/client/src/customData.ts b/extensions/css-language-features/client/src/customData.ts
index 25cc95ccc92..c9954de8c51 100644
--- a/extensions/css-language-features/client/src/customData.ts
+++ b/extensions/css-language-features/client/src/customData.ts
@@ -4,11 +4,11 @@
  *--------------------------------------------------------------------------------------------*/
 
 import * as path from 'path';
-import { workspace, WorkspaceFolder } from 'vscode';
+import { workspace, WorkspaceFolder, extensions } from 'vscode';
 
 interface ExperimentalConfig {
 	experimental?: {
-		customData?: string[]
+		customData?: string[];
 	};
 }
 
@@ -28,7 +28,6 @@ export function getCustomDataPathsInAllWorkspaces(workspaceFolders: WorkspaceFol
 			wfCSSConfig.workspaceFolderValue.experimental &&
 			wfCSSConfig.workspaceFolderValue.experimental.customData
 		) {
-
 			wfCSSConfig.workspaceFolderValue.experimental.customData.forEach(p => [
 				dataPaths.push(path.resolve(wf.uri.fsPath, p))
 			]);
@@ -37,3 +36,20 @@ export function getCustomDataPathsInAllWorkspaces(workspaceFolders: WorkspaceFol
 
 	return dataPaths;
 }
+
+export function getCustomDataPathsFromAllExtensions(): string[] {
+	const dataPaths: string[] = [];
+
+	for (const extension of extensions.all) {
+		const contributes = extension.packageJSON && extension.packageJSON.contributes;
+
+		if (contributes && contributes.css && contributes.css.customData && Array.isArray(contributes.css.customData)) {
+			const relativePaths: string[] = contributes.css.customData;
+			relativePaths.forEach(rp => {
+				dataPaths.push(path.resolve(extension.extensionPath, rp));
+			});
+		}
+	}
+
+	return dataPaths;
+}