diff --git a/src/utils/EntityTransformer.ts b/src/utils/EntityTransformer.ts
index bcaac5d..eac7008 100644
--- a/src/utils/EntityTransformer.ts
+++ b/src/utils/EntityTransformer.ts
@@ -41,6 +41,10 @@ export class EntityTransformer {
     props: EsPropsMetaDataInterface[],
     meta: EsMetaDataInterface,
   ) {
+    if (!entity) {
+      return undefined;
+    }
+
     if (entity instanceof Array) {
       return entity.map((entityItem) => {
         return this.normalizeProps(entityItem, props, meta);
diff --git a/test/fixtures/TestingClassOptionalNested.ts b/test/fixtures/TestingClassOptionalNested.ts
new file mode 100644
index 0000000..6801689
--- /dev/null
+++ b/test/fixtures/TestingClassOptionalNested.ts
@@ -0,0 +1,23 @@
+import { EsEntity } from '../../src/decorators/EsEntity';
+import { EsId } from '../../src/decorators/EsId';
+import { EsProperty } from '../../src/decorators/EsProperty';
+
+export class MyOptionalNestedEntity {
+  @EsProperty('keyword')
+  public name: string;
+}
+
+@EsEntity('elastic_index')
+export class MyRootEntityWithOptionalNested {
+  @EsId()
+  public id: string;
+
+  @EsProperty('integer')
+  public foo: number;
+
+  @EsProperty({ type: 'nested', entity: MyOptionalNestedEntity })
+  public nestedItem?: MyOptionalNestedEntity;
+
+  @EsProperty({ type: 'nested', entity: MyOptionalNestedEntity })
+  public nestedItems?: MyOptionalNestedEntity[];
+}
diff --git a/test/integration/Repository.integration.ts b/test/integration/Repository.integration.ts
index 324132b..2b9dec4 100644
--- a/test/integration/Repository.integration.ts
+++ b/test/integration/Repository.integration.ts
@@ -264,10 +264,8 @@ describe('Repository.integration', () => {
       error = e;
     }
     expect(error).toBeInstanceOf(EsException);
-    expect((error.originalError as ElasticsearchClientError).message).toBe(
-      'parse_exception\n' +
-        '\tRoot causes:\n' +
-        '\t\tparse_exception: request body is required',
+    expect((error.originalError as ElasticsearchClientError).message).toContain(
+      'request body is required',
     );
   });
 
diff --git a/test/integration/RepositoryAliases.integration.ts b/test/integration/RepositoryAliases.integration.ts
index 46734d2..ea0fc9d 100644
--- a/test/integration/RepositoryAliases.integration.ts
+++ b/test/integration/RepositoryAliases.integration.ts
@@ -202,10 +202,8 @@ describe('RepositoryAliases', () => {
       error = e;
     }
     expect(error).toBeInstanceOf(EsException);
-    expect((error.originalError as ResponseError).message).toBe(
-      'parse_exception\n' +
-        '\tRoot causes:\n' +
-        '\t\tparse_exception: request body is required',
+    expect((error.originalError as ResponseError).message).toContain(
+      'request body is required',
     );
   });
 
diff --git a/test/unit/src/utils/EntityTransformer.spec.ts b/test/unit/src/utils/EntityTransformer.spec.ts
index 96c3767..c78eae9 100644
--- a/test/unit/src/utils/EntityTransformer.spec.ts
+++ b/test/unit/src/utils/EntityTransformer.spec.ts
@@ -3,6 +3,7 @@ import { TestingClass as TestingClass2 } from '../../../fixtures/TestingClass2';
 import { EntityTransformer } from '../../../../src/utils/EntityTransformer';
 import { FactoryProvider } from '../../../../src/factory/Factory.provider';
 import { CustomIdGeneratorEntity } from '../../../fixtures/CustomIdGeneratorEntity';
+import { MyRootEntityWithOptionalNested } from '../../../fixtures/TestingClassOptionalNested';
 
 describe('entity transformer', () => {
   let entityTransformer: EntityTransformer;
@@ -68,4 +69,40 @@ describe('entity transformer', () => {
 
     expect(normalizedEntity.id).toBe('myCustomId');
   });
+
+  it('should work for nested entities - optional fields', () => {
+    const testingClass1 = new MyRootEntityWithOptionalNested();
+    testingClass1.id = '25u46fhno';
+    testingClass1.foo = 1;
+    const normalizedEntity = entityTransformer.normalize(testingClass1);
+    expect(normalizedEntity.id).toBe('25u46fhno');
+    expect(normalizedEntity.data.foo).toBe(1);
+    expect(normalizedEntity.data.nestedItem).toBeUndefined();
+    expect(normalizedEntity.data.nestedItems).toBeUndefined();
+
+    const denormalizedEntity = entityTransformer.denormalize(
+      MyRootEntityWithOptionalNested,
+      normalizedEntity,
+    );
+
+    // remove in future, clean the expected object in-case undefined affects properties
+    for (const [k, v] of Object.entries(testingClass1)) {
+      if (v === undefined) {
+        delete testingClass1[k];
+      }
+    }
+
+    expect(denormalizedEntity).toMatchObject(testingClass1);
+
+    // remove in future
+    for (const [k, v] of Object.entries(normalizedEntity.data)) {
+      if (v === undefined) {
+        delete normalizedEntity.data[k];
+      }
+    }
+
+    const normalizedEntityRetried =
+      entityTransformer.normalize(denormalizedEntity);
+    expect(normalizedEntityRetried).toMatchObject(normalizedEntity);
+  });
 });