diff --git a/Code/Mantid/MantidPlot/src/ApplicationWindow.cpp b/Code/Mantid/MantidPlot/src/ApplicationWindow.cpp
index 8b73140797265d501b27a031d6dc7a61f8be3cbf..56424d704a3ebe5cf4feef7b48c4250752a22f2c 100644
--- a/Code/Mantid/MantidPlot/src/ApplicationWindow.cpp
+++ b/Code/Mantid/MantidPlot/src/ApplicationWindow.cpp
@@ -6473,7 +6473,11 @@ AssociationsDialog* ApplicationWindow::showPlotAssociations(int curve)
   if (!w)
     return 0;
 
-  Graph *g = dynamic_cast<MultiLayer*>(w)->activeGraph();
+  auto ml = dynamic_cast<MultiLayer*>(w);
+  if(!ml)
+    return 0;
+
+  Graph *g = ml->activeGraph();
   if (!g)
     return 0;