gd command doesn't go to definition of identifier

I a *test* file tmp.tex consisting solely of the following LaTeX code:

Start LaTeX code
----------------
\DeclareAcronym{myacro}{
short = MYACRO,
long = some longer expansion of myacro
}

\section
{Big long section name that never ends but keeps going and going and}
\subsection{\ac{myacro}}
--------------
End LaTeX code

If I place my cursor on "myacro" on the last line and press "gd" (without quotes), cursor does not jump to the first occurance on the first line. However, if I attach the 4th last line "{Big long section..." to the preceding line "\section" with no adjoining space, then "gd" *does* work.

Can anyone explain why? The problem exhibits itself even if the file is named tmp.txt, so it doesn't seem to be a language-specific syntax issue.

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