diff --git a/Src/FdoUi/InflectionFeatureEditor.cs b/Src/FdoUi/InflectionFeatureEditor.cs
index 0b284feda5..0ec1d5fbb5 100644
--- a/Src/FdoUi/InflectionFeatureEditor.cs
+++ b/Src/FdoUi/InflectionFeatureEditor.cs
@@ -255,7 +255,7 @@ private void m_pOSPopupTreeManager_AfterSelect(object sender, System.Windows.For
 			// Arrange to turn all relevant items blue.
 			// Remember which item was selected so we can later 'doit'.
 			var hvoNode = e.Node as HvoTreeNode;
-			m_notSure = (string)hvoNode.Tag == "NotSure";
+			m_notSure = (string)hvoNode?.Tag == "NotSure";
 			if (hvoNode == null || hvoNode.Hvo == 0)
 			{
 				m_selectedHvo = 0;