Opera and Explorer Mac bug - absolute layer above iframe

An absolute layer positioned on top of an iframe will always disappear behind the iframe, even if you set its z-index.

Below you see an absolutely positioned layer (white) that should be on top of the iframe. In Opera and Explorer Mac it is positioned underneath the iframe, despite my z-index: 10.

Test

Text text text text text text
Text text text text text text
Text text text text text text
Text text text text text text
Text text text text text text
Text text text text text text