Using tikzexternalize with pdflscape results in rotated image

Question

When using the external TikZ library to externalize an image in a pdflscape landscape environment, the resulting image is rotated by 90 degrees. This does not happen when including "normal" images. How can I avoid this? Or is there another way to have a single landscape page in a PDF that is also displayed in landscape mode in the viewer?

I want the document to look the same, whether \tikzexternalize is active or not, so just wrapping the tikzpicture in \rotatebox{90} is, unfortunately, not an option.

In my real document, only one page is in landscape mode, so unfortunately I can't just use the landscape option of the documentclass. Also, I'm using memoir for my actual document, in case that makes a difference for the solution.

MWE:

\documentclass{article}
\usepackage{pdflscape}
\usepackage{mwe} % For the example image
\usepackage{tikz}
\usetikzlibrary{external}
\tikzexternalize % Without externalization, the orientation is correct
\tikzset{external/force remake}


\begin{document}
\lipsum[1-5]
  \begin{landscape}
    \includegraphics[width=4cm]{example-image-a}
    \begin{tikzpicture}
      \node [scale=5] {A};
    \end{tikzpicture}
  \end{landscape}
\end{document}

Output with \tikzexternalize commented out: Everything's fine

With \tikzexternalize uncommented: The TikZ A is rotated incorrectly:

Answer 1

The main difference between the original lscape and pdflscape is (I think, I don't know the latter so well:-) that pdflscape inserts code get the viewer to keep the page orientation in the viewer, but if your viewer is using heuristics to do this automatically (acrobat by default_ then this may not be needed and the two may conflict.