diff --git a/src/plugins/projectexplorer/task.cpp b/src/plugins/projectexplorer/task.cpp
index 91e6d5c987b..5849601ca0a 100644
--- a/src/plugins/projectexplorer/task.cpp
+++ b/src/plugins/projectexplorer/task.cpp
@@ -83,10 +83,10 @@ Task Task::buildConfigurationMissingTask()
                 Constants::TASK_CATEGORY_BUILDSYSTEM);
 }
 
-void Task::addMark(TextEditor::TextMark *mark)
+void Task::setMark(TextEditor::TextMark *mark)
 {
+    QTC_ASSERT(mark, return);
     QTC_ASSERT(m_mark.isNull(), return);
-
     m_mark = QSharedPointer<TextEditor::TextMark>(mark);
 }
 
diff --git a/src/plugins/projectexplorer/task.h b/src/plugins/projectexplorer/task.h
index 592bef9cab7..af8126c40eb 100644
--- a/src/plugins/projectexplorer/task.h
+++ b/src/plugins/projectexplorer/task.h
@@ -37,6 +37,8 @@
 
 namespace ProjectExplorer {
 
+class TaskHub;
+
 // Documentation inside.
 class PROJECTEXPLORER_EXPORT Task
 {
@@ -66,7 +68,6 @@ public:
     int movedLine = -1; // contains a line number if the line was moved in the editor
     Core::Id category;
     QIcon icon;
-    void addMark(TextEditor::TextMark *mark);
 
     // Having a QList<QTextLayout::FormatRange> in Task isn't that great
     // It would be cleaner to split up the text into
@@ -79,8 +80,12 @@ public:
     QList<QTextLayout::FormatRange> formats;
 
 private:
+    void setMark(TextEditor::TextMark *mark);
+
     QSharedPointer<TextEditor::TextMark> m_mark;
     static unsigned int s_nextId;
+
+    friend class TaskHub;
 };
 
 bool PROJECTEXPLORER_EXPORT operator==(const Task &t1, const Task &t2);
diff --git a/src/plugins/projectexplorer/taskhub.cpp b/src/plugins/projectexplorer/taskhub.cpp
index 2ce383bc6b2..16b2f7dd9a3 100644
--- a/src/plugins/projectexplorer/taskhub.cpp
+++ b/src/plugins/projectexplorer/taskhub.cpp
@@ -134,6 +134,8 @@ void TaskHub::addTask(Task task)
 {
     QTC_ASSERT(m_registeredCategories.contains(task.category), return);
     QTC_ASSERT(!task.description.isEmpty(), return);
+    QTC_ASSERT(!task.isNull(), return);
+    QTC_ASSERT(task.m_mark.isNull(), return);
 
     if (task.file.isEmpty())
         task.line = -1;
@@ -146,7 +148,7 @@ void TaskHub::addTask(Task task)
         auto mark = new TaskMark(task.taskId, task.file.toString(), task.line, task.type, !task.icon.isNull());
         mark->setIcon(task.icon);
         mark->setPriority(TextEditor::TextMark::LowPriority);
-        task.addMark(mark);
+        task.setMark(mark);
     }
     emit m_instance->taskAdded(task);
 }