diff --git a/doc/sphinxext/related_software.py b/doc/sphinxext/related_software.py
index d1df773b380..d1c29f74446 100644
--- a/doc/sphinxext/related_software.py
+++ b/doc/sphinxext/related_software.py
@@ -5,6 +5,10 @@
 1. Add it to the MNE-installers if possible, and it will automatically appear.
 2. If it's on PyPI and not in the MNE-installers, add it to the PYPI_PACKAGES set.
 3. If it's not on PyPI, add it to the MANUAL_PACKAGES dictionary.
+
+If PyPI or manual, also add package name to `related_software.txt` or
+`related_software_nodeps.txt` so that it's installed at doc-build time (for package
+metadata querying).
 """
 
 # Authors: The MNE-Python contributors.
@@ -35,6 +39,7 @@
     "niseq",
     "sesameeg",
     "mne-kit-gui",  # moved to its own env in the installers
+    "zuna",
 }
 
 # If it's not available on PyPI, add it to this dict:
@@ -221,7 +226,7 @@ def run(self):
         return [my_list]
 
 
-def setup(app):
+def setup(app):  # noqa: D103
     app.add_directive("related-software", RelatedSoftwareDirective)
     # Run it as soon as this is added as a Sphinx extension so that any errors
     # / new packages are reported early. The next call in run() will be cached.
diff --git a/doc/sphinxext/related_software_nodeps.txt b/doc/sphinxext/related_software_nodeps.txt
index 45c216d72dd..2b2e0c68945 100644
--- a/doc/sphinxext/related_software_nodeps.txt
+++ b/doc/sphinxext/related_software_nodeps.txt
@@ -4,3 +4,4 @@ fsleyes
 mne-kit-gui
 mne-videobrowser
 hedtools  # because it limits our Pandas version currently
+zuna  # requires pytorch