diff --git a/extensions/npm/src/main.ts b/extensions/npm/src/main.ts
index 29cfd32d14b..38935c2c68a 100644
--- a/extensions/npm/src/main.ts
+++ b/extensions/npm/src/main.ts
@@ -15,15 +15,37 @@ const localize = nls.loadMessageBundle();
 
 import { addJSONProviders } from './features/jsonContributions';
 import { NpmScriptsTreeDataProvider } from './npmView';
-import { NpmTaskDefinition, ScriptValidator } from './tasks';
+import { NpmTaskDefinition, ScriptValidator, isWorkspaceFolder } from './tasks';
 
 type AutoDetect = 'on' | 'off';
 let taskProvider: vscode.Disposable | undefined;
 
 class Validator implements ScriptValidator {
-	async scriptIsValid(_task: vscode.Task): Promise<boolean> {
-		// let tasks = await provideNpmScriptsForFolder(packageUri); 
-		return true;
+	async scriptIsValid(task: vscode.Task): Promise<boolean> {
+		let uri: vscode.Uri | null = this.getPackageJsonUri(task);
+		if (uri) {
+			let tasks = await provideNpmScriptsForFolder(uri);
+			for (let i = 0; i < tasks.length; i++) {
+				const t = tasks[i];
+				if (isWorkspaceFolder(task.scope) && isWorkspaceFolder(task.scope)) {
+					if (t.name === task.name && t.scope === task.scope && (<vscode.ShellExecution>(t.execution)).commandLine === (<vscode.ShellExecution>(task.execution)).commandLine) {
+						return true;
+					}
+				}
+			}
+		}
+		return false;
+	}
+
+	getPackageJsonUri(task: vscode.Task): vscode.Uri | null {
+		if (isWorkspaceFolder(task.scope)) {
+			if (task.definition.path) {
+				return vscode.Uri.file(path.join(task.scope.uri.fsPath, task.definition.path, 'package.json'));
+			} else {
+				return vscode.Uri.file(path.join(task.scope.uri.fsPath, 'package.json'));
+			}
+		}
+		return null;
 	}
 }
 
diff --git a/extensions/npm/src/npmView.ts b/extensions/npm/src/npmView.ts
index fa00617ef46..cb0f455c048 100644
--- a/extensions/npm/src/npmView.ts
+++ b/extensions/npm/src/npmView.ts
@@ -8,7 +8,7 @@ import {
 	WorkspaceFolder, workspace, commands, window, EventEmitter, Event,
 	ThemeIcon, Uri, TextDocument, TaskProvider
 } from 'vscode';
-import { NpmTaskDefinition, ScriptValidator } from './tasks';
+import { NpmTaskDefinition, ScriptValidator, isWorkspaceFolder } from './tasks';
 import * as path from 'path';
 
 class Folder extends TreeItem {
@@ -45,7 +45,11 @@ class PackageJSON extends TreeItem {
 		this.folder = folder;
 		this.path = relativePath;
 		this.contextValue = 'packageJSON';
-		this.resourceUri = Uri.file(path.join(folder!.resourceUri!.fsPath, relativePath, packageName));
+		if (relativePath) {
+			this.resourceUri = Uri.file(path.join(folder!.resourceUri!.fsPath, relativePath, packageName));
+		} else {
+			this.resourceUri = Uri.file(path.join(folder!.resourceUri!.fsPath, packageName));
+		}
 		this.iconPath = ThemeIcon.File;
 	}
 
@@ -83,14 +87,15 @@ export class NpmScriptsTreeDataProvider implements TreeDataProvider<TreeItem> {
 		const subscriptions = context.subscriptions;
 		this.validator = validator;
 		this.taskProvider = taskProvider;
+
 		subscriptions.push(commands.registerCommand('npm.runScript', this.runScript, this));
 		subscriptions.push(commands.registerCommand('npm.openScript', this.openScript, this));
 		subscriptions.push(commands.registerCommand('npm.refresh', this.refresh, this));
 	}
 
-	private runScript(task: Task) {
-		if (!this.validator.scriptIsValid(task)) {
-			window.showErrorMessage(`Could not find script ${task.name}`);
+	private async runScript(task: Task) {
+		if (!await this.validator.scriptIsValid(task)) {
+			window.showErrorMessage(`Could not find script '${task.name}' or the script has changed. Try to refresh the view.`);
 			return;
 		}
 		workspace.executeTask(task);
@@ -147,10 +152,6 @@ export class NpmScriptsTreeDataProvider implements TreeDataProvider<TreeItem> {
 		return [];
 	}
 
-	private isWorkspaceFolder(value: any): value is WorkspaceFolder {
-		return value && typeof value !== 'number';
-	}
-
 	private buildTaskTree(tasks: Task[]): Folder[] | PackageJSON[] {
 		let folders: Map<String, Folder> = new Map();
 		let packages: Map<String, PackageJSON> = new Map();
@@ -159,7 +160,7 @@ export class NpmScriptsTreeDataProvider implements TreeDataProvider<TreeItem> {
 		let packageJson = null;
 
 		tasks.forEach(each => {
-			if (this.isWorkspaceFolder(each.scope)) {
+			if (isWorkspaceFolder(each.scope)) {
 				folder = folders.get(each.scope.name);
 				if (!folder) {
 					folder = new Folder(each.scope);
diff --git a/extensions/npm/src/tasks.ts b/extensions/npm/src/tasks.ts
index 24c4ba2e497..cb443e387b6 100644
--- a/extensions/npm/src/tasks.ts
+++ b/extensions/npm/src/tasks.ts
@@ -3,7 +3,7 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-import { TaskDefinition, Task } from 'vscode';
+import { TaskDefinition, Task, WorkspaceFolder } from 'vscode';
 
 export interface NpmTaskDefinition extends TaskDefinition {
 	script: string;
@@ -12,4 +12,8 @@ export interface NpmTaskDefinition extends TaskDefinition {
 
 export interface ScriptValidator {
 	scriptIsValid(task: Task): Promise<boolean>;
+}
+
+export function isWorkspaceFolder(value: any): value is WorkspaceFolder {
+	return value && typeof value !== 'number';
 }
\ No newline at end of file