diff --git a/common/make/Makefile.slides.rubber b/common/make/Makefile.slides.rubber
index 8174e22..1f3bac8 100644
--- a/common/make/Makefile.slides.rubber
+++ b/common/make/Makefile.slides.rubber
@@ -1,30 +1,30 @@
 # Depends: rubber
 
 DIR:=$(strip $(shell dirname $(realpath $(lastword $(MAKEFILE_LIST)))))
 ORGS = $(wildcard *.org)
 TEXHOS = $(patsubst %.org,%.handout.tex,$(ORGS))
 TEXS = $(patsubst %.org,%.tex,$(ORGS))
 PDFS = $(patsubst %.org,%.pdf,$(ORGS))
 
 export TEXINPUTS = :$(DIR)/../latex/
 
 all: $(PDFS)
 
 .PRECIOUS: $(TEXS)
 %.tex: %.org
 	../bin/export-org-to-beamer $<
 
 %.pdf: %.tex
 	rubber -m pdftex $<
 
 %.handout.tex: %.tex
 	sed 's/\\documentclass[[]/\\documentclass[handout,/' $< > $@
 
 clean: $(patsubst %,%/clean,$(TEXS) $(TEXHOS))
-       rm -f *.vrb
+	rm -f *.vrb
 
 %/clean:
 	if [ -f $* ]; then rubber -m pdftex --clean $* ; fi
 	rm -f $*
 
 distclean: clean