diff --git a/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssembler.java b/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssembler.java
index 046754a9e..6e951a13d 100644
--- a/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssembler.java
+++ b/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssembler.java
@@ -112,8 +112,12 @@ public class TaskRepresentationModelAssembler
 
   public Task toEntityModel(TaskRepresentationModel repModel) throws InvalidArgumentException {
     verifyCorrectCustomAttributesFormat(repModel);
-    TaskImpl task =
-        (TaskImpl) taskService.newTask(repModel.getWorkbasketSummary().getWorkbasketId());
+    TaskImpl task;
+    if (repModel.getWorkbasketSummary() != null) {
+      task = (TaskImpl) taskService.newTask(repModel.getWorkbasketSummary().getWorkbasketId());
+    } else {
+      task = (TaskImpl) taskService.newTask();
+    }
     task.setId(repModel.getTaskId());
     task.setExternalId(repModel.getExternalId());
     task.setCreated(repModel.getCreated());
@@ -130,7 +134,9 @@ public class TaskRepresentationModelAssembler
     task.setState(repModel.getState());
     task.setClassificationSummary(
         classificationAssembler.toEntityModel(repModel.getClassificationSummary()));
-    task.setWorkbasketSummary(workbasketAssembler.toEntityModel(repModel.getWorkbasketSummary()));
+    if (repModel.getWorkbasketSummary() != null) {
+      task.setWorkbasketSummary(workbasketAssembler.toEntityModel(repModel.getWorkbasketSummary()));
+    }
     task.setBusinessProcessId(repModel.getBusinessProcessId());
     task.setParentBusinessProcessId(repModel.getParentBusinessProcessId());
     task.setOwner(repModel.getOwner());
diff --git a/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssembler.java b/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssembler.java
index 0e8a90f07..a4a5afd30 100644
--- a/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssembler.java
+++ b/rest/taskana-rest-spring/src/main/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssembler.java
@@ -116,8 +116,10 @@ public class TaskSummaryRepresentationModelAssembler
     taskSummary.setState(repModel.getState());
     taskSummary.setClassificationSummary(
         classificationAssembler.toEntityModel(repModel.getClassificationSummary()));
-    taskSummary.setWorkbasketSummary(
-        workbasketAssembler.toEntityModel(repModel.getWorkbasketSummary()));
+    if (repModel.getWorkbasketSummary() != null) {
+      taskSummary.setWorkbasketSummary(
+          workbasketAssembler.toEntityModel(repModel.getWorkbasketSummary()));
+    }
     taskSummary.setBusinessProcessId(repModel.getBusinessProcessId());
     taskSummary.setParentBusinessProcessId(repModel.getParentBusinessProcessId());
     taskSummary.setOwner(repModel.getOwner());
diff --git a/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssemberTest.java b/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssemberTest.java
index 6d033d046..025217e53 100644
--- a/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssemberTest.java
+++ b/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskRepresentationModelAssemberTest.java
@@ -116,6 +116,35 @@ class TaskRepresentationModelAssemberTest {
     testEquality(task, repModel);
   }
 
+  @Test
+  void should_ReturnEntity_When_ConvertingRepresentationModelWithoutWorkbasketSummaryToEntity()
+      throws Exception {
+    // given
+    ObjectReferenceRepresentationModel primaryObjRef = new ObjectReferenceRepresentationModel();
+    primaryObjRef.setId("abc");
+    ClassificationSummaryRepresentationModel classificationSummary =
+        new ClassificationSummaryRepresentationModel();
+    classificationSummary.setKey("keyabc");
+    classificationSummary.setDomain("DOMAIN_A");
+    classificationSummary.setType("MANUAL");
+    AttachmentRepresentationModel attachment = new AttachmentRepresentationModel();
+    attachment.setClassificationSummary(classificationSummary);
+    attachment.setAttachmentId("attachmentId");
+    attachment.setObjectReference(primaryObjRef);
+    TaskRepresentationModel repModel = new TaskRepresentationModel();
+    repModel.setTaskId("taskId");
+    repModel.setExternalId("externalId");
+    repModel.setClassificationSummary(classificationSummary);
+    repModel.setPrimaryObjRef(primaryObjRef);
+    // when
+    Task task = assembler.toEntityModel(repModel);
+    // then
+    assertThat(repModel.getWorkbasketSummary()).isNull();
+    assertThat(task.getWorkbasketSummary())
+        .isNotNull()
+        .hasAllNullFieldsOrPropertiesExcept("markedForDeletion");
+  }
+
   @Test
   void should_ReturnRepresentationModel_When_ConvertingEntityToRepresentationModel()
       throws Exception {
diff --git a/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssemblerTest.java b/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssemblerTest.java
index e51ac53e0..7397d26aa 100644
--- a/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssemblerTest.java
+++ b/rest/taskana-rest-spring/src/test/java/pro/taskana/task/rest/assembler/TaskSummaryRepresentationModelAssemblerTest.java
@@ -186,6 +186,34 @@ class TaskSummaryRepresentationModelAssemblerTest {
     testEquality(task, repModel);
   }
 
+  @Test
+  void should_ReturnEntity_When_ConvertingRepresentationModelWithoutWorkbasketSummaryToEntity() {
+    // given
+    ObjectReferenceRepresentationModel primaryObjRef = new ObjectReferenceRepresentationModel();
+    primaryObjRef.setId("abc");
+    ClassificationSummaryRepresentationModel classificationSummary =
+        new ClassificationSummaryRepresentationModel();
+    classificationSummary.setKey("keyabc");
+    classificationSummary.setDomain("DOMAIN_A");
+    classificationSummary.setType("MANUAL");
+    AttachmentRepresentationModel attachment = new AttachmentRepresentationModel();
+    attachment.setClassificationSummary(classificationSummary);
+    attachment.setAttachmentId("attachmentId");
+    attachment.setObjectReference(primaryObjRef);
+    TaskRepresentationModel repModel = new TaskRepresentationModel();
+    repModel.setTaskId("taskId");
+    repModel.setExternalId("externalId");
+    repModel.setClassificationSummary(classificationSummary);
+    repModel.setPrimaryObjRef(primaryObjRef);
+    // when
+    TaskSummary taskSummary = assembler.toEntityModel(repModel);
+    // then
+    assertThat(repModel.getWorkbasketSummary()).isNull();
+    assertThat(taskSummary.getWorkbasketSummary())
+        .isNotNull()
+        .hasAllNullFieldsOrPropertiesExcept("markedForDeletion");
+  }
+
   @Test
   void should_Equal_When_ComparingEntityWithConvertedEntity() {
     // given