Incorrect reference to enumerate list items

Question

In the following MWE \ref{a} and \ref{aa} show 1 and 2a instead of 1.1 and 1.2.1, respectively. I wonder how this can be fixed.

\documentclass{article}

\usepackage{enumerate}

\renewcommand{\labelenumi}{\thesection.\arabic{enumi}}
\renewcommand{\labelenumii}{\thesection.\arabic{enumi}.\arabic{enumii}}

\begin{document}

\section{Section Title}

Item \ref{a} and Item \ref{aa}.

\begin{enumerate}
\item \label{a} A
\item B

\begin{enumerate}
\item \label{aa} AA
\item BB
\end{enumerate}
\end{enumerate}

\end{document}

Answer 1

Here is a version with enumitem and its \setlist command. The figures 1 and 2 refer to the nesting level, 1 is enumi then.

\documentclass{article}

\usepackage{enumitem}

\setlist[enumerate,1]{label={\arabic*}}
\setlist[enumerate,2]{label={\theenumi\alph*}}

\begin{document}

\section{Section Title}

Item \ref{a} and Item \ref{aa}.
\begin{enumerate}
\item \label{a} A
\item B
\begin{enumerate}
\item \label{aa} AA
\item BB
\end{enumerate}
\end{enumerate}
\end{document}