diff --git a/slides_template/fonts.tex b/slides_template/fonts.tex
new file mode 100644
index 0000000..747563b
--- /dev/null
+++ b/slides_template/fonts.tex
@@ -0,0 +1,19 @@
+% Font setup shared by the slides and by the notes pages that mknotes
+% typesets, so that the two match. Loaded by example.tex directly and passed
+% to mknotes with --preamble.
+%
+% Requires fontspec, which unicode-math pulls in on the slides side. Paths must
+% stay relative to the document directory: LuaTeX fails to resolve a
+% parent-relative Path= and dies with an unhelpful empty-filename error.
+
+\setsansfont{OpenSans}[
+  Path = fonts/OpenSans/, Extension = .ttf,
+  UprightFont = *-Regular, BoldFont = *-Bold,
+  ItalicFont = *-Italic, BoldItalicFont = *-BoldItalic]
+
+\setmonofont{RobotoMono}[
+  Path = fonts/RobotoMono/, Extension = .ttf,
+  UprightFont = *-Regular, BoldFont = *-Bold,
+  ItalicFont = *-Italic, BoldItalicFont = *-BoldItalic]
+
+\renewcommand{\familydefault}{\sfdefault}
diff --git a/slides_template/mknotes b/slides_template/mknotes
index f6a9118..7ecb1f4 100755
--- a/slides_template/mknotes
+++ b/slides_template/mknotes
@@ -151,6 +151,10 @@ def attach_notes(pages, notes):
 #: Side margin on the generated notes pages, as a fraction of the page.
 HMARGIN = 0.06
 
+#: Font setup shared with the slides. Used when it exists, so that the notes
+#: match the deck without anyone having to remember a flag.
+DEFAULT_PREAMBLE = "fonts.tex"
+
 # The page is laid out by hand rather than by geometry: the header band runs
 # full bleed to the top and outer edges to meet the thumbnail, so the margins
 # have to be applied per element instead of to the page.
@@ -159,11 +163,13 @@ NOTES_PREAMBLE = r"""\documentclass{article}
   margin=0bp]{geometry}
 \usepackage{parskip}
 \usepackage{xcolor}
+\usepackage{fontspec}
 \definecolor{notegrey}{RGB}{230,230,230}
 \pagestyle{empty}
 \setlength{\parindent}{0pt}
 \setlength{\fboxsep}{0pt}
 \setlength{\topskip}{0pt}
+%(preamble)s
 \begin{document}
 """
 
@@ -179,7 +185,7 @@ def escape_for_context(text):
 
 
 def build_notes_pdf(pages, width, height, thumb_w, thumb_h, workdir,
-                    jobname="notes"):
+                    preamble=None, jobname="notes"):
     """Typeset one notes page per slide page and return the resulting PDF path.
 
     The page is made at the size it will actually occupy in the finished sheet,
@@ -198,7 +204,14 @@ def build_notes_pdf(pages, width, height, thumb_w, thumb_h, workdir,
     textwidth = width - hmargin * 2
     bandwidth = width - thumb_w
 
-    body = [NOTES_PREAMBLE % {"width": width, "height": height}]
+    # \input rather than the file's contents, so that anything relative inside
+    # it (font paths, say) resolves against the document directory. LaTeX runs
+    # from there even though its output goes to the working directory.
+    extra = r"\input{%s}" % preamble if preamble else ""
+
+    body = [NOTES_PREAMBLE % {
+        "width": width, "height": height, "preamble": extra,
+    }]
 
     total = len(pages)
     for index, page in enumerate(pages):
@@ -249,9 +262,12 @@ def build_notes_pdf(pages, width, height, thumb_w, thumb_h, workdir,
     with open(source, "w", encoding="utf-8") as handle:
         handle.write("\n".join(body) + "\n")
 
+    # Run from the document directory so relative paths in the preamble resolve,
+    # but send the output elsewhere so the build leaves nothing behind.
     result = subprocess.run(
-        ["lualatex", "-interaction=nonstopmode", "-halt-on-error", jobname + ".tex"],
-        cwd=workdir, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
+        ["lualatex", "-interaction=nonstopmode", "-halt-on-error",
+         "-output-directory=" + workdir, source],
+        stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
     )
     output = os.path.join(workdir, jobname + ".pdf")
     if result.returncode != 0 or not os.path.exists(output):
@@ -294,6 +310,10 @@ def main():
                         help="base name of the build, e.g. 'example'")
     parser.add_argument("--output",
                         help="output file (default: <jobname>-notes.pdf)")
+    parser.add_argument("--preamble", metavar="FILE", default=DEFAULT_PREAMBLE,
+                        help="LaTeX fragment to \\input into the notes pages, "
+                             "so they can share the slides' font setup "
+                             f"(default: {DEFAULT_PREAMBLE} when it exists)")
     parser.add_argument("--thumb-scale", type=float, default=0.29,
                         metavar="F",
                         help="slide thumbnail size on the notes half, as a "
@@ -321,10 +341,19 @@ def main():
     width, height = float(box.width), float(box.height)
     thumb = max(0.0, min(args.thumb_scale, 0.9))
 
+    # A preamble named on the command line has to be there; the default one is
+    # a convenience and is skipped when the document does not use it.
+    preamble = args.preamble
+    if preamble and not os.path.exists(preamble):
+        if preamble != DEFAULT_PREAMBLE:
+            raise SystemExit(f"mknotes: {preamble} not found")
+        preamble = None
+
     workdir = tempfile.mkdtemp(prefix="mknotes-")
     try:
         notes_pdf = PdfReader(build_notes_pdf(
-            pages, width, height, width * thumb, height * thumb, workdir))
+            pages, width, height, width * thumb, height * thumb, workdir,
+            preamble=preamble))
         writer = assemble_notes(slides, notes_pdf, width, height, thumb)
 
         output = args.output or f"{args.jobname}-notes.pdf"