diff --git a/contrib/src/gizmos/splittree.cpp b/contrib/src/gizmos/splittree.cpp
index fbb3885081..a99b6733c8 100644
--- a/contrib/src/gizmos/splittree.cpp
+++ b/contrib/src/gizmos/splittree.cpp
@@ -427,7 +427,7 @@ void wxTreeCompanionWindow::OnPaint(wxPaintEvent& event)
 			dc.DrawLine(0, cy, clientSize.x, cy);
 		}
 	}
-	if (m_treeCtrl->GetBoundingRect(lastH, itemRect))
+	if (lastH.IsOk() && m_treeCtrl->GetBoundingRect(lastH, itemRect))
 	{
 		cy = itemRect.GetBottom();
 		dc.DrawLine(0, cy, clientSize.x, cy);