diff --git a/.github/workflows/makefile.yml b/.github/workflows/makefile.yml
index f8d8d33..862c8df 100644
--- a/.github/workflows/makefile.yml
+++ b/.github/workflows/makefile.yml
@@ -7,7 +7,7 @@ env:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     concurrency:
       group: ci-${{ github.ref_name }}
       cancel-in-progress: true
diff --git a/Makefile b/Makefile
index 200d7c2..378314c 100755
--- a/Makefile
+++ b/Makefile
@@ -3,6 +3,7 @@ TEMPLATES = templates
 BUILDDIR  = build
 
 PDFENGINE = lualatex
+PDFENGINE_OPT = --shell-escape
 
 SOURCES=$(wildcard $(SOURCEDIR)/*.md)
 SLIDES=$(patsubst $(SOURCEDIR)/%.md,$(BUILDDIR)/%.html,$(SOURCES))
@@ -56,6 +57,7 @@ $(PDFS): $(BUILDDIR)/%.pdf : $(SOURCEDIR)/%.md
 			-f markdown+emoji \
 			-t latex \
 			--pdf-engine=$(PDFENGINE) \
+			--pdf-engine-opt=$(PDFENGINE_OPT) \
 			--lua-filter=meta.lua \
 			--lua-filter=english.lua \
 			--citeproc \