Emphasis in syntax highlighting is lost when colorscheme is reconfigured

[bongbang]

To replicate:

1. Load the minimal example below.
2. :set background=dark (it doesn't matter if the background is already dark)
3. Notice that the content of \emph is no longer italicized.
4. <local-leader>lx to get the italics back.

The problem also occurs when the color scheme is switched by the :colo command.

\documentclass{article}
\begin{document}
Watch this \emph{emphasis}.
\end{document}

[lervag]

I believe this is fixed now.