diff --git a/include/osgWidget/Frame b/include/osgWidget/Frame
index a0f05d886..b33c79a83 100644
--- a/include/osgWidget/Frame
+++ b/include/osgWidget/Frame
@@ -95,7 +95,7 @@ class OSGWIDGET_EXPORT Frame: public Table
             Corner (const Corner&, const osg::CopyOp&);
 
             virtual void parented  (Window*);
-            virtual bool mouseDrag (double, double, WindowManager*);
+            virtual bool mouseDrag (double, double, const WindowManager*);
 
             CornerType getCornerType() const
             {
@@ -128,7 +128,7 @@ class OSGWIDGET_EXPORT Frame: public Table
 
             virtual void parented   (Window*);
             virtual void positioned ();
-            virtual bool mouseDrag  (double, double, WindowManager*);
+            virtual bool mouseDrag  (double, double, const WindowManager*);
 
             BorderType getBorderType() const
             {
diff --git a/src/osgWidget/Frame.cpp b/src/osgWidget/Frame.cpp
index 507a1a4d6..612e97b22 100644
--- a/src/osgWidget/Frame.cpp
+++ b/src/osgWidget/Frame.cpp
@@ -50,7 +50,7 @@ void Frame::Corner::parented(Window* window) {
     if(parent->canResize()) setEventMask(EVENT_MASK_MOUSE_DRAG);
 }
 
-bool Frame::Corner::mouseDrag(double x, double y, WindowManager* wm)
+bool Frame::Corner::mouseDrag(double x, double y, const WindowManager* wm)
 {
     Frame* parent = dynamic_cast<Frame*>(getParent());
 
@@ -137,7 +137,7 @@ void Frame::Border::positioned()
     }
 }
 
-bool Frame::Border::mouseDrag(double x, double y, WindowManager* wm)
+bool Frame::Border::mouseDrag(double x, double y, const WindowManager* wm)
 {
     Frame* parent = dynamic_cast<Frame*>(getParent());