         subview.removeConstraint(widthConstraint!)
         
         if isOpen {
-            lastWidth = paneView.frame.size.width
+            lastExtent = paneView.frame.size.width
         } else {
             subview.frame.size.width = 0
         }

        toggleSubview(self.rightView,
                      dividerIndex: 1,
                      paneView: infoPane.view,
                      lastWidth: &lastInfoWidth,
                      collapseRightward: true,
                      widthConstraint: infoWidthConstraint)
    }

        toggleSubview(self.leftView,
                      dividerIndex: 0,
                      paneView: sourceList.view,
                      lastExtent: &lastSourceWidth,
                      collapseRightward: false,
                      widthConstraint: sourceWidthConstraint)
    }
