diff --git a/Charts/Core/vtkPlotBag.cxx b/Charts/Core/vtkPlotBag.cxx
index 58dd4d5fc530eb504bf3b4c8b3ff3cbf37db55f6..6a7ef5d1f2f7232b6fd33132a071b93176cf5f52 100644
--- a/Charts/Core/vtkPlotBag.cxx
+++ b/Charts/Core/vtkPlotBag.cxx
@@ -371,8 +371,14 @@ vtkStdString vtkPlotBag::GetTooltipLabel(const vtkVector2d &plotPos,
           vtkAbstractArray *colName = vtkAbstractArray::SafeDownCast(
             this->GetInput()->GetColumnByName("ColName"));
           std::stringstream ss;
-          ss << (!colName ? "?" :
-            colName->GetVariantValue(seriesIndex).ToString());
+          if (colName)
+            {
+            ss << colName->GetVariantValue(seriesIndex).ToString();
+            }
+          else
+            {
+            ss << "?";
+            }
           tooltipLabel += ss.str();
           }
           break;