diff --git a/src/map/imgmap.cpp b/src/map/imgmap.cpp
index 9293f714..33077095 100644
--- a/src/map/imgmap.cpp
+++ b/src/map/imgmap.cpp
@@ -260,13 +260,6 @@ void IMGMap::unload()
 	_data->clear();
 }
 
-QRectF IMGMap::bounds()
-{
-	RectD prect(_data->bounds(), _projection);
-	return QRectF(_transform.proj2img(prect.topLeft()),
-	  _transform.proj2img(prect.bottomRight()));
-}
-
 int IMGMap::zoomFit(const QSize &size, const RectC &rect)
 {
 	if (rect.isValid()) {
@@ -320,6 +313,10 @@ Transform IMGMap::transform(int zoom) const
 void IMGMap::updateTransform()
 {
 	_transform = transform(_zoom);
+
+	RectD prect(_data->bounds(), _projection);
+	_bounds = QRectF(_transform.proj2img(prect.topLeft()),
+	  _transform.proj2img(prect.bottomRight()));
 }
 
 QPointF IMGMap::ll2xy(const Coordinates &c)
diff --git a/src/map/imgmap.h b/src/map/imgmap.h
index 03dec65b..1618fe36 100644
--- a/src/map/imgmap.h
+++ b/src/map/imgmap.h
@@ -18,7 +18,7 @@ public:
 
 	QString name() const {return _data->name();}
 
-	QRectF bounds();
+	QRectF bounds() {return _bounds;}
 
 	virtual int zoom() const {return _zoom;}
 	virtual void setZoom(int zoom);
@@ -62,6 +62,7 @@ private:
 	int _zoom;
 	Projection _projection;
 	Transform _transform;
+	QRectF _bounds;
 
 	bool _valid;
 	QString _errorString;