diff --git a/src/qwt_plot_axis.cpp b/src/qwt_plot_axis.cpp
index a49882fa..523f5edd 100644
--- a/src/qwt_plot_axis.cpp
+++ b/src/qwt_plot_axis.cpp
@@ -770,14 +770,14 @@ void QwtPlot::updateAxes()
         {
             const QRectF rect = item->boundingRect();
 
-            if ( rect.width() >= 0.0 )
+            if ( isAxisValid( item->xAxis()) && rect.width() >= 0.0 )
             {
                 const QwtAxisId xAxis = item->xAxis();
                 boundingIntervals[ xAxis.pos ][ xAxis.id ] |=
                     QwtInterval( rect.left(), rect.right() );
             }
 
-            if ( rect.height() >= 0.0 )
+            if ( isAxisValid( item->yAxis()) && rect.height() >= 0.0 )
             {
                 const QwtAxisId yAxis = item->yAxis();
                 boundingIntervals[ yAxis.pos ][ yAxis.id ] |=
@@ -831,7 +831,8 @@ void QwtPlot::updateAxes()
     for ( it = itmList.begin(); it != itmList.end(); ++it )
     {
         QwtPlotItem* item = *it;
-        if ( item->testItemInterest( QwtPlotItem::ScaleInterest ) )
+        if ( item->testItemInterest( QwtPlotItem::ScaleInterest ) &&
+             isAxisValid( item->xAxis() ) && isAxisValid( item->yAxis() ) )
         {
             item->updateScaleDiv( axisScaleDiv( item->xAxis() ),
                 axisScaleDiv( item->yAxis() ) );
diff --git a/src/qwt_plot_curve.cpp b/src/qwt_plot_curve.cpp
index 7abd4e4b..c7ddddf2 100644
--- a/src/qwt_plot_curve.cpp
+++ b/src/qwt_plot_curve.cpp
@@ -1055,6 +1055,9 @@ int QwtPlotCurve::closestPoint( const QPointF& pos, double* dist ) const
     if ( plot() == NULL || numSamples <= 0 )
         return -1;
 
+    if ( !plot()->isAxisValid( xAxis() ) || !plot()->isAxisValid( yAxis() ) )
+        return -1;
+
     const QwtSeriesData< QPointF >* series = data();
 
     const QwtScaleMap xMap = plot()->canvasMap( xAxis() );