diff --git a/src/plugins/projectexplorer/task.cpp b/src/plugins/projectexplorer/task.cpp
index 462e7e6d07c..74995d2b321 100644
--- a/src/plugins/projectexplorer/task.cpp
+++ b/src/plugins/projectexplorer/task.cpp
@@ -29,6 +29,8 @@
 
 #include "task.h"
 
+#include <utils/qtcassert.h>
+
 namespace ProjectExplorer
 {
 
@@ -68,6 +70,8 @@ Task::Task(TaskType type_, const QString &description_,
 
 void Task::addMark(TextEditor::BaseTextMark *mark)
 {
+    QTC_ASSERT(m_mark.isNull(), return);
+
     m_mark = QSharedPointer<TextEditor::BaseTextMark>(mark);
 }
 
diff --git a/src/plugins/projectexplorer/taskhub.cpp b/src/plugins/projectexplorer/taskhub.cpp
index 990734c09c1..eb3a9e15eb2 100644
--- a/src/plugins/projectexplorer/taskhub.cpp
+++ b/src/plugins/projectexplorer/taskhub.cpp
@@ -35,6 +35,7 @@
 using namespace ProjectExplorer;
 
 TaskHub *m_instance = 0;
+QSet<Core::Id> TaskHub::m_registededCategories;
 
 class TaskMark : public TextEditor::BaseTextMark
 {
@@ -99,6 +100,7 @@ TaskHub::~TaskHub()
 void TaskHub::addCategory(Core::Id categoryId, const QString &displayName, bool visible)
 {
     QTC_CHECK(!displayName.isEmpty());
+    QTC_ASSERT(!m_registededCategories.contains(categoryId), return);
     emit m_instance->categoryAdded(categoryId, displayName, visible);
 }
 
@@ -114,6 +116,16 @@ void TaskHub::addTask(Task::TaskType type, const QString &description, Core::Id
 
 void TaskHub::addTask(Task task)
 {
+    QTC_ASSERT(m_registededCategories.contains(task.category), return);
+    QTC_ASSERT(!task.description.isEmpty(), return);
+
+    if (task.file.isEmpty())
+        task.line = -1;
+
+    if (task.line <= 0)
+        task.line = -1;
+    task.movedLine = task.line;
+
     if (task.line != -1 && !task.file.isEmpty()) {
         TaskMark *mark = new TaskMark(task.taskId, task.file.toString(), task.line, !task.icon.isNull());
         mark->setIcon(task.icon);
@@ -128,6 +140,7 @@ void TaskHub::addTask(Task task)
 
 void TaskHub::clearTasks(Core::Id categoryId)
 {
+    QTC_ASSERT(m_registededCategories.contains(categoryId), return);
     emit m_instance->tasksCleared(categoryId);
 }
 
@@ -158,6 +171,7 @@ void TaskHub::showTaskInEditor(unsigned int id)
 
 void TaskHub::setCategoryVisibility(const Core::Id &categoryId, bool visible)
 {
+    QTC_ASSERT(m_registededCategories.contains(categoryId), return);
     emit m_instance->categoryVisibilityChanged(categoryId, visible);
 }
 
diff --git a/src/plugins/projectexplorer/taskhub.h b/src/plugins/projectexplorer/taskhub.h
index 77cc75bf68e..5edd12fc7ed 100644
--- a/src/plugins/projectexplorer/taskhub.h
+++ b/src/plugins/projectexplorer/taskhub.h
@@ -85,6 +85,8 @@ private:
     const QIcon m_errorIcon;
     const QIcon m_warningIcon;
 
+    static QSet<Core::Id> m_registededCategories;
+
     friend class ProjectExplorerPlugin;
 };