diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index 2324162060a4191c8990367862eb9a2831bf91ee..28b7f5ae205778ae75139dbcea1c3057c0f8805b 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -1626,6 +1626,7 @@ export class ProcessExecution implements vscode.ProcessExecution {
 		if (typeof process !== 'string') {
 			throw illegalArgument('process');
 		}
+		this._args = [];
 		this._process = process;
 		if (varg1 !== undefined) {
 			if (Array.isArray(varg1)) {
@@ -1635,9 +1636,6 @@ export class ProcessExecution implements vscode.ProcessExecution {
 				this._options = varg1;
 			}
 		}
-		if (this._args === undefined) {
-			this._args = [];
-		}
 	}
 
 
@@ -1689,9 +1687,9 @@ export class ProcessExecution implements vscode.ProcessExecution {
 @es5ClassCompat
 export class ShellExecution implements vscode.ShellExecution {
 
-	private _commandLine: string;
-	private _command: string | vscode.ShellQuotedString;
-	private _args: (string | vscode.ShellQuotedString)[];
+	private _commandLine: string | undefined;
+	private _command: string | vscode.ShellQuotedString | undefined;
+	private _args: (string | vscode.ShellQuotedString)[] = [];
 	private _options: vscode.ShellExecutionOptions | undefined;
 
 	constructor(commandLine: string, options?: vscode.ShellExecutionOptions);
@@ -1717,7 +1715,7 @@ export class ShellExecution implements vscode.ShellExecution {
 	}
 
 	get commandLine(): string {
-		return this._commandLine;
+		return this._commandLine ? this._commandLine : '';
 	}
 
 	set commandLine(value: string) {
@@ -1728,7 +1726,7 @@ export class ShellExecution implements vscode.ShellExecution {
 	}
 
 	get command(): string | vscode.ShellQuotedString {
-		return this._command;
+		return this._command ? this._command : '';
 	}
 
 	set command(value: string | vscode.ShellQuotedString) {
@@ -1826,23 +1824,23 @@ export class Task implements vscode.Task2 {
 	constructor(definition: vscode.TaskDefinition, name: string, source: string, execution?: ProcessExecution | ShellExecution | CustomExecution2, problemMatchers?: string | string[]);
 	constructor(definition: vscode.TaskDefinition, scope: vscode.TaskScope.Global | vscode.TaskScope.Workspace | vscode.WorkspaceFolder, name: string, source: string, execution?: ProcessExecution | ShellExecution | CustomExecution2, problemMatchers?: string | string[]);
 	constructor(definition: vscode.TaskDefinition, arg2: string | (vscode.TaskScope.Global | vscode.TaskScope.Workspace) | vscode.WorkspaceFolder, arg3: any, arg4?: any, arg5?: any, arg6?: any) {
-		this.definition = definition;
+		this._definition = this.definition = definition;
 		let problemMatchers: string | string[];
 		if (typeof arg2 === 'string') {
-			this.name = arg2;
-			this.source = arg3;
+			this._name = this.name = arg2;
+			this._source = this.source = arg3;
 			this.execution = arg4;
 			problemMatchers = arg5;
 		} else if (arg2 === TaskScope.Global || arg2 === TaskScope.Workspace) {
 			this.target = arg2;
-			this.name = arg3;
-			this.source = arg4;
+			this._name = this.name = arg3;
+			this._source = this.source = arg4;
 			this.execution = arg5;
 			problemMatchers = arg6;
 		} else {
 			this.target = arg2;
-			this.name = arg3;
-			this.source = arg4;
+			this._name = this.name = arg3;
+			this._source = this.source = arg4;
 			this.execution = arg5;
 			problemMatchers = arg6;
 		}