diff --git a/extensions/vscode-api-tests/src/singlefolder-tests/workspace.tasks.test.ts b/extensions/vscode-api-tests/src/singlefolder-tests/workspace.tasks.test.ts
new file mode 100644
index 00000000000..67600f97cd6
--- /dev/null
+++ b/extensions/vscode-api-tests/src/singlefolder-tests/workspace.tasks.test.ts
@@ -0,0 +1,63 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as assert from 'assert';
+import * as vscode from 'vscode';
+
+suite.only('workspace-namespace', () => {
+
+	suite('Tasks', () => {
+
+		test('CustomExecution2 task should start and shutdown successfully', (done) => {
+			interface CustomTestingTaskDefinition extends vscode.TaskDefinition {
+				/**
+				 * One of the task properties. This can be used to customize the task in the tasks.json
+				 */
+				customProp1: string;
+			}
+			const taskType: string = 'customTesting';
+			const taskName = 'First custom task';
+			const reg1 = vscode.window.onDidOpenTerminal(term => {
+				reg1.dispose();
+				const reg2 = term.onDidWriteData(e => {
+					reg2.dispose();
+					assert.equal(e, 'testing\r\n');
+					term.dispose();
+				});
+			});
+			const exitEmitter = new vscode.EventEmitter<number>();
+			const taskProvider = vscode.tasks.registerTaskProvider(taskType, {
+				provideTasks: () => {
+					let result: vscode.Task[] = [];
+					let kind: CustomTestingTaskDefinition = {
+						type: taskType,
+						customProp1: 'testing task one'
+					};
+					const writeEmitter = new vscode.EventEmitter<string>();
+					let execution = new vscode.CustomExecution2((): Thenable<vscode.TerminalVirtualProcess> => {
+						return Promise.resolve(<vscode.TerminalVirtualProcess>{
+							onDidWrite: writeEmitter.event,
+							start: () => {
+								writeEmitter.fire('testing\r\n');
+							},
+							onDidExit: exitEmitter.event,
+							shutdown: () => {
+								taskProvider.dispose();
+								done();
+							}
+						});
+					});
+					let task = new vscode.Task2(kind, vscode.TaskScope.Workspace, taskName, taskType, execution);
+					result.push(task);
+					return result;
+				},
+				resolveTask(_task: vscode.Task): vscode.Task | undefined {
+					return undefined;
+				}
+			});
+			vscode.commands.executeCommand('workbench.action.tasks.runTask', `${taskType}: ${taskName}`);
+		});
+	});
+});
diff --git a/src/vs/workbench/api/node/extHostTask.ts b/src/vs/workbench/api/node/extHostTask.ts
index a1e82957b48..0e7f5f9dd7a 100644
--- a/src/vs/workbench/api/node/extHostTask.ts
+++ b/src/vs/workbench/api/node/extHostTask.ts
@@ -588,7 +588,7 @@ export class ExtHostTask implements ExtHostTaskShape {
 
 			// Clone the custom execution to keep the original untouched. This is important for multiple runs of the same task.
 			this._activeCustomExecutions2.set(execution.id, execution2);
-			this._terminalService.attachVirtualProcessToTerminal(terminalId, await execution2.callback());
+			await this._terminalService.attachVirtualProcessToTerminal(terminalId, await execution2.callback());
 		}
 
 		// Once a terminal is spun up for the custom execution task this event will be fired.
diff --git a/src/vs/workbench/api/node/extHostTerminalService.ts b/src/vs/workbench/api/node/extHostTerminalService.ts
index 35884b08ba4..847bba891e8 100644
--- a/src/vs/workbench/api/node/extHostTerminalService.ts
+++ b/src/vs/workbench/api/node/extHostTerminalService.ts
@@ -337,8 +337,8 @@ export class ExtHostTerminalService implements ExtHostTerminalServiceShape {
 		return terminal;
 	}
 
-	public attachVirtualProcessToTerminal(id: number, virtualProcess: vscode.TerminalVirtualProcess) {
-		const terminal = this._getTerminalById(id);
+	public async attachVirtualProcessToTerminal(id: number, virtualProcess: vscode.TerminalVirtualProcess): Promise<void> {
+		const terminal = this._getTerminalByIdEventually(id);
 		if (!terminal) {
 			throw new Error(`Cannot resolve terminal with id ${id} for virtual process`);
 		}
@@ -619,6 +619,10 @@ export class ExtHostTerminalService implements ExtHostTerminalServiceShape {
 	}
 
 	public async $startVirtualProcess(id: number, initialDimensions: ITerminalDimensionsDto | undefined): Promise<void> {
+		// Make sure the ExtHostTerminal exists so onDidOpenTerminal has fired before we call
+		// TerminalVirtualProcess.start
+		await this._getTerminalByIdEventually(id);
+
 		// Processes should be initialized here for normal virtual process terminals, however for
 		// tasks they are responsible for attaching the virtual process to a terminal so this
 		// function may be called before tasks is able to attach to the terminal.