diff --git a/AppKit/Platform/DOM/CPPlatformWindow+DOM.j b/AppKit/Platform/DOM/CPPlatformWindow+DOM.j
index b0610b5f2..f39c6f5c8 100644
--- a/AppKit/Platform/DOM/CPPlatformWindow+DOM.j
+++ b/AppKit/Platform/DOM/CPPlatformWindow+DOM.j
@@ -1280,7 +1280,7 @@ var PreventScroll = true;
             insertionIndex = _windowLevels[middle] > aLevel ? middle : middle + 1
 
         [_windowLevels insertObject:aLevel atIndex:insertionIndex];
-        layer._DOMElement.style.zIndex = aLevel;
+        layer._DOMElement.style.zIndex = aLevel + 1;
 
         _DOMBodyElement.appendChild(layer._DOMElement);
     }