# Duplicate book titles in index [duplicate]

I have a weird problem with \makeindex that I cannot resolve. Here is a minimal example:

\documentclass[12pt,letterpaper,twoside]{memoir}
\newcommand{\defn}{\textit}
\begin{document}
Autopoiesis, developed by Humberto  Maturana\footnote{H. R. Maturana and F. Varela (1973)  \textit{De M\'aquinas y Seres Vivos}\index{maqui@\textit{M\'aquinas y Seres Vivos, de}}, Editorial Universitaria, Santiago, Chile.\label{maq}}\footnote{H. R. Maturana and F. Varela (1980) \textit{Autopoiesis and Cognition: the Realisation of the Living}
\index{AutopoiesisAnd@\textit{Autopoiesis and Cognition}}
D. Reidel Publishing Company, Dordrecht.\label{cogn}}
\textit{Autopoiesis and Cognition: the Realisation of the Living}\footref{cogn}
\index{AutopoiesisAnd@\textit{Autopoiesis and Cognition}} are the original sources for Humberto Maturana and Francisco Varela's autopoiesis.
\printindex
\end{document}


Both book titles appear twice in the index, even though I copied and pasted the \index entries. In the full example they are on different pages, but in the minimal example they are both on p. 1, but that doesn't stop them appearing twice. This does NOT happen with similar cases in the complete example.

The idx file looks like this:

\indexentry{maqui@\textit{M\'aquinas y Seres Vivos, de}}{1}
\indexentry{AutopoiesisAnd@\textit{Autopoiesis and Cognition}}{1}
\indexentry{maqui@\textit  {M\'aquinas y Seres Vivos, de}}{1}
\indexentry{AutopoiesisAnd@\textit  {Autopoiesis and Cognition}}{1}


In the third and fourth there is whitespace after \textit{, but in the first and second there isn't.