diff --git a/CHANGES b/CHANGES
index 1609cd3966b..2c28286ffe5 100644
--- a/CHANGES
+++ b/CHANGES
@@ -60,6 +60,9 @@ Features added
 Bugs fixed
 ----------
 
+* #10984: LaTeX: Document :confval:`latex_additional_files` behavior for files
+  with ``.tex`` extension.
+
 Testing
 --------
 
diff --git a/doc/latex.rst b/doc/latex.rst
index e7f631aafc7..8e97ff2c16a 100644
--- a/doc/latex.rst
+++ b/doc/latex.rst
@@ -207,6 +207,9 @@ Keys that you may want to override include:
 
       latex_additional_files = ["mystyle.sty"]
 
+   Do not use ``.tex`` as suffix, else the file is submitted itself to the PDF
+   build process, use ``.tex.txt`` or ``.sty`` as in the examples above.
+
    Default: ``''``
 
 ``'figure_align'``
diff --git a/doc/usage/configuration.rst b/doc/usage/configuration.rst
index 4ddd16a0e93..a3c2c8f516e 100644
--- a/doc/usage/configuration.rst
+++ b/doc/usage/configuration.rst
@@ -2372,6 +2372,15 @@ These options influence LaTeX output.
    You have to make sure yourself that the filenames don't collide with those
    of any automatically copied files.
 
+   .. attention::
+
+      Filenames with extension ``.tex`` will automatically be handed over to
+      the PDF build process triggered by :option:`sphinx-build -M`
+      ``latexpdf`` or by :program:`make latexpdf`.  If the file was added only
+      to be ``\input{}`` from a modified preamble, you must add a further
+      suffix such as ``.txt`` to the filename and adjust accordingly the
+      ``\input{}`` command added to the LaTeX document preamble.
+
    .. versionadded:: 0.6
 
    .. versionchanged:: 1.2