diff --git a/.latexmkrc b/.latexmkrc
index d42fb95..e87380c 100644
--- a/.latexmkrc
+++ b/.latexmkrc
@@ -1,4 +1,3 @@
 $pdflatex="pdflatex -shell-escape -interaction=nonstopmode -synctex=1 %O %S";
 $out_dir = 'build';
 $pdf_mode = 1;
-
diff --git a/Makefile b/Makefile
index 26928d3..ce1f1a9 100644
--- a/Makefile
+++ b/Makefile
@@ -5,15 +5,15 @@ HANDOUTS := $(patsubst build/presentation_%.pdf,build/presentation_%_handout.pdf
 all: $(PRESENTATIONS) $(HANDOUTS)
 
 build/presentation_%.pdf: src/%/presentation.tex build/prepared
-	TEXINPUTS=./lib/cel-slides-template-2025:$$TEXINPUTS latexmk $<
+	TEXINPUTS=./lib/cel-slides-template-2025:$(dir $<):$$TEXINPUTS latexmk $<
 	mv build/presentation.pdf $@
 
 build/presentation_%_handout.pdf: src/%/presentation.tex build/prepared
-	TEXINPUTS=./lib/cel-slides-template-2025:$$TEXINPUTS latexmk -pdflatex='pdflatex %O "\def\ishandout{1}\input{%S}"' $<
+	TEXINPUTS=./lib/cel-slides-template-2025:$(dir $<):$$TEXINPUTS latexmk -pdflatex='pdflatex %O "\def\ishandout{1}\input{%S}"' $<
 	mv build/presentation.pdf $@
 
 build/prepared:
-	mkdir -p build
+	mkdir build
 	touch build/prepared
 
 .PHONY: clean
diff --git a/src/2026-01-16/presentation.tex b/src/2026-01-16/presentation.tex
index 3bd1187..ede842f 100644
--- a/src/2026-01-16/presentation.tex
+++ b/src/2026-01-16/presentation.tex
@@ -30,7 +30,7 @@
 \usepackage{tikz}
 \usepackage{tikz-3dplot}
 \usetikzlibrary{spy, external, intersections, positioning}
-%\tikzexternalize[prefix=build/]
+\tikzexternalize
 
 \usepackage{pgfplots}
 \pgfplotsset{compat=newest}