[tex-live] Bug when using \nabla with \pdfgentounicode=1

[FX]

Dear list members,

I seem to experience a bug in the current texlive distribution. I reduced it to the following short testcase:

\documentclass{article}
\usepackage{mathptmx}
\pdfgentounicode=1
\begin{document}
$\nabla$
\end{document}


When this document is compiled, pdflatex errors out saying:

pdfTeX warning: pdflatex: No flags specified for non-embedded font `Times-Roman' (ptmr8r) (I'm using 34): fix your map entry.
pdfTeX warning: pdflatex: No flags specified for non-embedded font `Symbol' (psyr) (I'm using 4): fix your map entry.
../../../texk/web2c/pdftexdir/writefont.c:536: failed assertion `fo->fd->builtin_glyph_names != NULL'


>From my reading of the archives, it appears that the two warnings are unrelated, known issues in the pdftex core. The last one, however, causes pdflatex to stop compiling and fails to produce a document.

All three elements are needed to produce this: the mathptmx package, using pdfgentounicode and including the \nabla symbol. I don't know which one is behaving unexpectedly, causing the core to error out.


I hope someone can shed some light into this, or even fix it.

Best regards,
FXC