diff --git a/src/external-worker-client.spec.ts b/src/external-worker-client.spec.ts
index 53fed33..1e8307d 100644
--- a/src/external-worker-client.spec.ts
+++ b/src/external-worker-client.spec.ts
@@ -75,6 +75,50 @@ describe('ExternalWorkerClient', () => {
             expect(job).toBeDefined();
         });
 
+
+        it('and complete job with promise', async () => {
+            const scope = nockInstance
+              .post(`/external-job-api/acquire/jobs`, {
+                  topic: "myTopic",
+                  lockDuration: "PT1M",
+                  numberOfTasks: 1,
+                  numberOfRetries: 5,
+                  workerId: "test-worker",
+                  scopeType: null
+              })
+              .reply(200, acquireJobResponse)
+              .post(`/external-job-api/acquire/jobs`, {
+                  topic: "myTopic",
+                  lockDuration: "PT1M",
+                  numberOfTasks: 1,
+                  numberOfRetries: 5,
+                  workerId: "test-worker",
+                  scopeType: null
+              })
+              .reply(200, [])
+              .post(`/external-job-api/acquire/jobs/${acquireJobResponse[0].id}/complete`, {
+                  variables: null,
+                  workerId: "test-worker"
+              })
+              .reply(204);
+
+            let job: ExternalWorkerAcquireJobResponse = undefined;
+            const subscription = externalWorkerClient.subscribe({
+                topic: 'myTopic',
+                callbackHandler(acquiredJob: ExternalWorkerAcquireJobResponse, workResultBuilder: WorkerResultBuilder) {
+                    job = acquiredJob;
+                    return Promise.resolve(workResultBuilder.success());
+                },
+                waitPeriodSeconds: 0.2
+            });
+            const done = await waitForRequestsToComplete(scope);
+            expect(done).toBeTruthy();
+
+            subscription.unsubscribe();
+            scope.done();
+            expect(job).toBeDefined();
+        });
+
         it('and complete job with variables', async () => {
             const scope = nockInstance
                 .post(`/external-job-api/acquire/jobs`, {
@@ -161,6 +205,50 @@ describe('ExternalWorkerClient', () => {
             expect(job).toBeDefined();
         });
 
+        it('and fail job with promise', async () => {
+            const scope = nockInstance
+                .post(`/external-job-api/acquire/jobs`, {
+                    topic: "myTopic",
+                    lockDuration: "PT1M",
+                    numberOfTasks: 1,
+                    numberOfRetries: 5,
+                    workerId: "test-worker",
+                    scopeType: null
+                })
+                .reply(200, acquireJobResponse)
+                .post(`/external-job-api/acquire/jobs`, {
+                    topic: "myTopic",
+                    lockDuration: "PT1M",
+                    numberOfTasks: 1,
+                    numberOfRetries: 5,
+                    workerId: "test-worker",
+                    scopeType: null
+                })
+                .reply(200, [])
+                .post(`/external-job-api/acquire/jobs/${acquireJobResponse[0].id}/fail`, {
+                    workerId: "test-worker",
+                    errorMessage: "Some error message"
+                })
+                .reply(204);
+
+            let job: ExternalWorkerAcquireJobResponse = undefined;
+            const subscription = externalWorkerClient.subscribe({
+                topic: 'myTopic',
+                callbackHandler(acquiredJob: ExternalWorkerAcquireJobResponse, workResultBuilder: WorkerResultBuilder) {
+                    job = acquiredJob;
+                    return Promise.reject("Some error message");
+                },
+                waitPeriodSeconds: 0.2
+            });
+
+            const done = await waitForRequestsToComplete(scope);
+            expect(done).toBeTruthy();
+
+            subscription.unsubscribe();
+            scope.done();
+            expect(job).toBeDefined();
+        });
+
         it('and bpmn error job', async () => {
             const scope = nockInstance
                 .post(`/external-job-api/acquire/jobs`, {
diff --git a/src/external-worker-client.ts b/src/external-worker-client.ts
index 12b1a43..3d29d1a 100644
--- a/src/external-worker-client.ts
+++ b/src/external-worker-client.ts
@@ -43,15 +43,15 @@ export class ExternalWorkerClient {
             for (const job of jobs) {
                 const jobId = job.id;
                 try {
-                    const workResult = params.callbackHandler(job, new WorkerResultBuilder(job));
-                    if (!workResult) {
+                    const workResult = await Promise.resolve(params.callbackHandler(job, new WorkerResultBuilder(job)));
+                    if (!workResult || !workResult.execute) {
                         await this._restClient.completeJob({jobId});
                     } else {
                         await workResult.execute(this._restClient);
                     }
                 } catch (e) {
                     console.error('Failed to execute job with exception', e);
-                    await this._restClient.failJob({jobId, errorDetails: JSON.stringify(e)});
+                    await this._restClient.failJob({jobId, errorMessage: typeof e === 'string' ? e : JSON.stringify(e)});
                 }
             }
             if (timeoutInformation.unsubscribed) {
@@ -211,7 +211,7 @@ export type ExternalWorkerClientParams = {
 
 export type ExternalWorkerSubscriptionParams = {
     topic: string;
-    callbackHandler: (acquiredJob: ExternalWorkerAcquireJobResponse, workResultBuilder?: WorkerResultBuilder) => WorkResult | void,
+    callbackHandler: (acquiredJob: ExternalWorkerAcquireJobResponse, workResultBuilder: WorkerResultBuilder) => WorkResult | Promise<WorkResult> | void,
     lockDuration?: string;
     numberOfRetries?: number;
     numberOfTasks?: number;