Set a transparent icon in beamer's bibliography

I want to \uncover a citation in a particular overlay. The problem is that the bibliography's item icon (article in this case) is not set as transparent, but the text is.

How can I make the icon transparent also?

Here is the MWE:

\documentclass{beamer}

\begin{document}

\begin{frame}
\setbeamercovered{transparent}

\begin{thebibliography}{1}
\uncover<1>{
    \setbeamertemplate{bibliography item}[article]
    \bibitem{}
    \scriptsize Doe, J. (1975).
    \newblock\scriptsize Title of the first paper.
    \newblock {\em Journal.}
}
\uncover<1-2>{
    \setbeamertemplate{bibliography item}[article]
    \bibitem{}
    \scriptsize Doe, J. (1980).
    \newblock\scriptsize Title of the second paper.
    \newblock {\em Journal.}
}
\end{thebibliography}

\end{frame}

\end{document}

And here is the output: