diff --git a/extensions/npm/src/main.ts b/extensions/npm/src/main.ts
index 82d266687f8..a52b9de7cb3 100644
--- a/extensions/npm/src/main.ts
+++ b/extensions/npm/src/main.ts
@@ -123,7 +123,7 @@ async function getNpmScriptsAsTasks(): Promise<vscode.Task[]> {
 			result.push(task);
 		});
 		// add some 'well known' npm tasks
-		result.push(new vscode.Task({ type: 'npm', script: 'install' } as NpmTaskDefinition, `install`, 'npm', new vscode.ShellExecution(`npm install`)));
+		result.push(new vscode.Task({ type: 'npm', script: 'install' } as NpmTaskDefinition, `install`, 'npm', new vscode.ShellExecution(`npm install`), []));
 		return Promise.resolve(result);
 	} catch (e) {
 		return Promise.resolve(emptyTasks);
diff --git a/src/vs/workbench/api/node/extHostTask.ts b/src/vs/workbench/api/node/extHostTask.ts
index e6bd17c90d4..36195a1b02a 100644
--- a/src/vs/workbench/api/node/extHostTask.ts
+++ b/src/vs/workbench/api/node/extHostTask.ts
@@ -352,7 +352,8 @@ namespace Tasks {
 			group: task.group ? (task.group as types.TaskGroup).id : undefined,
 			command: command,
 			isBackground: !!task.isBackground,
-			problemMatchers: task.problemMatchers.slice()
+			problemMatchers: task.problemMatchers.slice(),
+			hasDefinedMatchers: (task as types.Task).hasDefinedMatchers
 		};
 		return result;
 	}
diff --git a/src/vs/workbench/api/node/extHostTypes.ts b/src/vs/workbench/api/node/extHostTypes.ts
index 51c7e0b2934..ee87589d753 100644
--- a/src/vs/workbench/api/node/extHostTypes.ts
+++ b/src/vs/workbench/api/node/extHostTypes.ts
@@ -1158,6 +1158,7 @@ export class Task implements vscode.Task {
 	private _name: string;
 	private _execution: ProcessExecution | ShellExecution;
 	private _problemMatchers: string[];
+	private _hasDefinedMatchers: boolean;
 	private _isBackground: boolean;
 	private _source: string;
 	private _group: TaskGroup;
@@ -1170,10 +1171,13 @@ export class Task implements vscode.Task {
 		this.execution = execution;
 		if (typeof problemMatchers === 'string') {
 			this._problemMatchers = [problemMatchers];
+			this._hasDefinedMatchers = true;
 		} else if (Array.isArray(problemMatchers)) {
 			this._problemMatchers = problemMatchers;
+			this._hasDefinedMatchers = true;
 		} else {
 			this._problemMatchers = [];
+			this._hasDefinedMatchers = false;
 		}
 		this._isBackground = false;
 	}
@@ -1227,9 +1231,16 @@ export class Task implements vscode.Task {
 
 	set problemMatchers(value: string[]) {
 		if (!Array.isArray(value)) {
-			value = [];
+			this._problemMatchers = [];
+			this._hasDefinedMatchers = false;
+			return;
 		}
 		this._problemMatchers = value;
+		this._hasDefinedMatchers = true;
+	}
+
+	get hasDefinedMatchers(): boolean {
+		return this._hasDefinedMatchers;
 	}
 
 	get isBackground(): boolean {
diff --git a/src/vs/workbench/parts/tasks/common/tasks.ts b/src/vs/workbench/parts/tasks/common/tasks.ts
index 43b7cd5a77b..04c51da7beb 100644
--- a/src/vs/workbench/parts/tasks/common/tasks.ts
+++ b/src/vs/workbench/parts/tasks/common/tasks.ts
@@ -340,6 +340,8 @@ export interface ContributedTask extends CommonTask, ConfigurationProperties {
 
 	defines: TaskIdentifier;
 
+	hasDefinedMatchers: boolean;
+
 	/**
 	 * The command configuration
 	 */
diff --git a/src/vs/workbench/parts/tasks/electron-browser/task.contribution.ts b/src/vs/workbench/parts/tasks/electron-browser/task.contribution.ts
index 4c63c3bbcc5..c339df79443 100644
--- a/src/vs/workbench/parts/tasks/electron-browser/task.contribution.ts
+++ b/src/vs/workbench/parts/tasks/electron-browser/task.contribution.ts
@@ -856,7 +856,7 @@ class TaskService extends EventEmitter implements ITaskService {
 			return false;
 		}
 		if (task._source.config === void 0 && ContributedTask.is(task)) {
-			return true;
+			return !task.hasDefinedMatchers && task.problemMatchers.length === 0;
 		}
 		let configProperties: TaskConfig.ConfigurationProperties = task._source.config.element;
 		return configProperties.problemMatcher === void 0;