Place the QED symbol for a proof that ends with a figure on the same line of the figure caption

Question

I have a figure at the end of a proof environment (see MWE below). I would like to have the QED symbol that ends the proof on the same line of the figure caption. Placing \qedhere after or inside \caption did not do it. Any suggestion is appreciated.

Thanks.

\documentclass{article}
\usepackage{amsthm,amssymb}
\usepackage{lipsum}

\renewcommand{\qedsymbol}{$\blacksquare$}

\begin{document}
    \begin{proof}
        \lipsum[1]
        \begin{figure}[h]
            \centering
            %\includegraphics{...}
            \caption{Figure caption.} \qedhere
        \end{figure}
    \end{proof} 
\end{document}

Answer 1

To illustrate Beeton's comment:

Note that the caption package adds an additonal \dp\strutbox to the bottom baseline.

\documentclass{article}
\usepackage{amsthm,amssymb}
%\usepackage{caption}
\usepackage{capt-of}
\usepackage{lipsum}

\renewcommand{\qedsymbol}{$\blacksquare$}

\begin{document}
    \begin{proof}
        \lipsum[1]
        \begin{minipage}[b]{0.9\textwidth}
            \centering
            %\includegraphics{...}
            \captionof{figure}{Figure caption.}%\vspace{-\dp\strutbox}
        \end{minipage}%\llap{\rule{0.9\textwidth}{0.5pt}}% show baseline
    \end{proof} 
\end{document}