diff --git a/lib/taskana-core/src/main/java/pro/taskana/task/internal/models/TaskImpl.java b/lib/taskana-core/src/main/java/pro/taskana/task/internal/models/TaskImpl.java
index c20e0e707..8de0de3b7 100644
--- a/lib/taskana-core/src/main/java/pro/taskana/task/internal/models/TaskImpl.java
+++ b/lib/taskana-core/src/main/java/pro/taskana/task/internal/models/TaskImpl.java
@@ -1,7 +1,6 @@
 package pro.taskana.task.internal.models;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -21,8 +20,8 @@ import pro.taskana.workbasket.internal.models.WorkbasketSummaryImpl;
 public class TaskImpl extends TaskSummaryImpl implements Task {
 
   // All objects have to be serializable
-  private Map<String, String> customAttributes = Collections.emptyMap();
-  private Map<String, String> callbackInfo = Collections.emptyMap();
+  private Map<String, String> customAttributes = new HashMap<>();
+  private Map<String, String> callbackInfo = new HashMap<>();
   private CallbackState callbackState;
   private List<Attachment> attachments = new ArrayList<>();
 
diff --git a/lib/taskana-core/src/test/java/acceptance/task/GetTaskAccTest.java b/lib/taskana-core/src/test/java/acceptance/task/GetTaskAccTest.java
index 7a5b16447..54dccb0e5 100644
--- a/lib/taskana-core/src/test/java/acceptance/task/GetTaskAccTest.java
+++ b/lib/taskana-core/src/test/java/acceptance/task/GetTaskAccTest.java
@@ -1,6 +1,7 @@
 package acceptance.task;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import acceptance.AbstractAccTest;
@@ -77,6 +78,8 @@ class GetTaskAccTest extends AbstractAccTest {
     assertThat(task.getCustomAttribute(TaskCustomField.CUSTOM_14)).isEqualTo("abc");
     assertThat(task.getCustomAttribute(TaskCustomField.CUSTOM_15)).isEqualTo("custom15");
     assertThat(task.getCustomAttribute(TaskCustomField.CUSTOM_16)).isEqualTo("custom16");
+    assertThatCode(() -> task.getCustomAttributeMap().put("X", "Y")).doesNotThrowAnyException();
+    assertThatCode(() -> task.getCallbackInfo().put("X", "Y")).doesNotThrowAnyException();
   }
 
   @WithAccessId(user = "user-1-1")
@@ -84,10 +87,7 @@ class GetTaskAccTest extends AbstractAccTest {
   void should_ThrowException_When_RequestedTaskByIdIsNotExisting() {
     TaskService taskService = taskanaEngine.getTaskService();
 
-    ThrowingCallable call =
-        () -> {
-          taskService.getTask("INVALID");
-        };
+    ThrowingCallable call = () -> taskService.getTask("INVALID");
     assertThatThrownBy(call).isInstanceOf(TaskNotFoundException.class);
   }
 
@@ -98,9 +98,7 @@ class GetTaskAccTest extends AbstractAccTest {
     TaskService taskService = taskanaEngine.getTaskService();
 
     ThrowingCallable getTaskCall =
-        () -> {
-          taskService.getTask("TKI:000000000000000000000000000000000000");
-        };
+        () -> taskService.getTask("TKI:000000000000000000000000000000000000");
     assertThatThrownBy(getTaskCall).isInstanceOf(NotAuthorizedException.class);
   }