diff --git a/src/plugins/diffeditor/diffeditor.h b/src/plugins/diffeditor/diffeditor.h
index 2f14635afac..e9582efcd68 100644
--- a/src/plugins/diffeditor/diffeditor.h
+++ b/src/plugins/diffeditor/diffeditor.h
@@ -51,9 +51,9 @@ namespace DiffEditor {
 namespace Internal {
 class DescriptionEditorWidget;
 class DiffEditorDocument;
+class DiffEditorGuiController;
 } // namespace Internal
 
-class DiffEditorGuiController;
 class SideBySideDiffEditorWidget;
 class UnifiedDiffEditorWidget;
 
@@ -104,7 +104,7 @@ private:
     SideBySideDiffEditorWidget *m_sideBySideEditor;
     UnifiedDiffEditorWidget *m_unifiedEditor;
     QWidget *m_currentEditor;
-    DiffEditorGuiController *m_guiController;
+    Internal::DiffEditorGuiController *m_guiController;
     QToolBar *m_toolBar;
     QComboBox *m_entriesComboBox;
     QAction *m_whitespaceButtonAction;
diff --git a/src/plugins/diffeditor/diffeditorguicontroller.cpp b/src/plugins/diffeditor/diffeditorguicontroller.cpp
index c32ded2eb57..c2885fb83ee 100644
--- a/src/plugins/diffeditor/diffeditorguicontroller.cpp
+++ b/src/plugins/diffeditor/diffeditorguicontroller.cpp
@@ -41,6 +41,7 @@ static const char horizontalScrollBarSynchronizationKeyC[] =
         "HorizontalScrollBarSynchronization";
 
 namespace DiffEditor {
+namespace Internal {
 
 DiffEditorGuiController::DiffEditorGuiController(
         DiffEditorController *controller,
@@ -138,4 +139,5 @@ void DiffEditorGuiController::setCurrentDiffFileIndex(int diffFileIndex)
     emit currentDiffFileIndexChanged(newIndex);
 }
 
+} // namespace Internal
 } // namespace DiffEditor
diff --git a/src/plugins/diffeditor/diffeditorguicontroller.h b/src/plugins/diffeditor/diffeditorguicontroller.h
index e5d155059bd..5c2eee87c0c 100644
--- a/src/plugins/diffeditor/diffeditorguicontroller.h
+++ b/src/plugins/diffeditor/diffeditorguicontroller.h
@@ -31,15 +31,15 @@
 #ifndef DIFFEDITORGUICONTROLLER_H
 #define DIFFEDITORGUICONTROLLER_H
 
-#include "diffeditor_global.h"
-
 #include <QObject>
 
 namespace DiffEditor {
 
 class DiffEditorController;
 
-class DIFFEDITOR_EXPORT DiffEditorGuiController : public QObject
+namespace Internal {
+
+class DiffEditorGuiController : public QObject
 {
     Q_OBJECT
 public:
@@ -72,6 +72,7 @@ private:
     int m_currentDiffFileIndex;
 };
 
+} // namespace Internal
 } // namespace DiffEditor
 
 #endif // DIFFEDITORGUICONTROLLER_H
diff --git a/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp b/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp
index 108cc0080cd..74804b348eb 100644
--- a/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp
+++ b/src/plugins/diffeditor/sidebysidediffeditorwidget.cpp
@@ -72,6 +72,8 @@ using namespace Utils;
 
 namespace DiffEditor {
 
+using namespace Internal;
+
 ////////////////////////
 /*
 class MultiHighlighter : public SyntaxHighlighter
diff --git a/src/plugins/diffeditor/sidebysidediffeditorwidget.h b/src/plugins/diffeditor/sidebysidediffeditorwidget.h
index 4ba741df1db..6d5493f985e 100644
--- a/src/plugins/diffeditor/sidebysidediffeditorwidget.h
+++ b/src/plugins/diffeditor/sidebysidediffeditorwidget.h
@@ -46,7 +46,8 @@ QT_END_NAMESPACE
 
 
 namespace DiffEditor {
-class DiffEditorGuiController;
+
+namespace Internal { class DiffEditorGuiController; }
 class SideDiffEditorWidget;
 class ChunkData;
 class FileData;
@@ -57,7 +58,7 @@ class DIFFEDITOR_EXPORT SideBySideDiffEditorWidget : public QWidget
 public:
     explicit SideBySideDiffEditorWidget(QWidget *parent = 0);
 
-    void setDiffEditorGuiController(DiffEditorGuiController *controller);
+    void setDiffEditorGuiController(Internal::DiffEditorGuiController *controller);
 
 private slots:
     void clear(const QString &message = QString());
@@ -95,7 +96,7 @@ private:
                             int lineNumber, int columnNumber);
     void patch(bool revert);
 
-    DiffEditorGuiController *m_guiController;
+    Internal::DiffEditorGuiController *m_guiController;
     DiffEditorController *m_controller;
     SideDiffEditorWidget *m_leftEditor;
     SideDiffEditorWidget *m_rightEditor;
diff --git a/src/plugins/diffeditor/unifieddiffeditorwidget.cpp b/src/plugins/diffeditor/unifieddiffeditorwidget.cpp
index 332667addf7..89a57447194 100644
--- a/src/plugins/diffeditor/unifieddiffeditorwidget.cpp
+++ b/src/plugins/diffeditor/unifieddiffeditorwidget.cpp
@@ -70,6 +70,8 @@ using namespace TextEditor;
 
 namespace DiffEditor {
 
+using namespace Internal;
+
 UnifiedDiffEditorWidget::UnifiedDiffEditorWidget(QWidget *parent)
     : SelectableTextEditorWidget("DiffEditor.UnifiedDiffEditor", parent)
     , m_guiController(0)
diff --git a/src/plugins/diffeditor/unifieddiffeditorwidget.h b/src/plugins/diffeditor/unifieddiffeditorwidget.h
index df780417029..13fe0ede933 100644
--- a/src/plugins/diffeditor/unifieddiffeditorwidget.h
+++ b/src/plugins/diffeditor/unifieddiffeditorwidget.h
@@ -48,7 +48,8 @@ QT_END_NAMESPACE
 
 namespace DiffEditor {
 
-class DiffEditorGuiController;
+namespace Internal { class DiffEditorGuiController; }
+
 class ChunkData;
 class FileData;
 
@@ -59,7 +60,7 @@ class DIFFEDITOR_EXPORT UnifiedDiffEditorWidget
 public:
     UnifiedDiffEditorWidget(QWidget *parent = 0);
 
-    void setDiffEditorGuiController(DiffEditorGuiController *controller);
+    void setDiffEditorGuiController(Internal::DiffEditorGuiController *controller);
 
 public slots:
     void setDisplaySettings(const TextEditor::DisplaySettings &ds);
@@ -113,7 +114,7 @@ private:
                                int chunkIndex);
     void patch(bool revert);
 
-    DiffEditorGuiController *m_guiController;
+    Internal::DiffEditorGuiController *m_guiController;
     DiffEditorController *m_controller;
 
     // block number, visual line number.