Prefix label greyed out when following component disabled

I have a problem where a prefix label in a custom inspector gets greyed out when only the first following component is disabled. How can I fix this? I have tried adding a pseudo-component with zero width before the disabled component, but it still takes up some spaces and creates a glitched look.

Example: http://i.imgur.com/xa6Nytt.png

Here you can see the prefix label turns grey because the following component is disabled, even when explicitly enabling the GUI beforehand:

 EditorGUILayout.BeginHorizontal ();
 GUI.enabled = true; // This has no effect
 EditorGUILayout.PrefixLabel ("Grid snapping");
 GUI.enabled = mb.gridOption > 0;
 bool decrement = GUILayout.Button ("-", layoutOptions);
 GUI.enabled = true;
 // ...
 EditorGUILayout.EndHorizontal ();

What might I be able to do about this?