diff --git a/src/vs/workbench/api/browser/mainThreadTask.ts b/src/vs/workbench/api/browser/mainThreadTask.ts
index 391cd0cef99a5e4cf7950820d09c11680ac8456d..2f4cb073c9fb9b51baed7596b1ec64fd1dcb45a7 100644
--- a/src/vs/workbench/api/browser/mainThreadTask.ts
+++ b/src/vs/workbench/api/browser/mainThreadTask.ts
@@ -53,7 +53,7 @@ namespace TaskProcessStartedDTO {
 }
 
 namespace TaskProcessEndedDTO {
-	export function from(value: TaskExecution, exitCode: number): TaskProcessEndedDTO {
+	export function from(value: TaskExecution, exitCode: number | undefined): TaskProcessEndedDTO {
 		return {
 			id: value.id,
 			exitCode
@@ -429,7 +429,7 @@ export class MainThreadTask implements MainThreadTaskShape {
 			} else if (event.kind === TaskEventKind.ProcessStarted) {
 				this._proxy.$onDidStartTaskProcess(TaskProcessStartedDTO.from(task.getTaskExecution(), event.processId!));
 			} else if (event.kind === TaskEventKind.ProcessEnded) {
-				this._proxy.$onDidEndTaskProcess(TaskProcessEndedDTO.from(task.getTaskExecution(), event.exitCode!));
+				this._proxy.$onDidEndTaskProcess(TaskProcessEndedDTO.from(task.getTaskExecution(), event.exitCode));
 			} else if (event.kind === TaskEventKind.End) {
 				this._proxy.$OnDidEndTask(TaskExecutionDTO.from(task.getTaskExecution()));
 			}
diff --git a/src/vs/workbench/api/common/shared/tasks.ts b/src/vs/workbench/api/common/shared/tasks.ts
index 17396177e5b44e43798d9becdc081b0f08d596e1..4de859f671b35939984834dc956f2db3d9c2804a 100644
--- a/src/vs/workbench/api/common/shared/tasks.ts
+++ b/src/vs/workbench/api/common/shared/tasks.ts
@@ -113,7 +113,7 @@ export interface TaskProcessStartedDTO {
 
 export interface TaskProcessEndedDTO {
 	id: string;
-	exitCode: number;
+	exitCode: number | undefined;
 }