diff --git a/doc/doxygen/Makefile b/doc/doxygen/Makefile
index 9d6c62b97bb1..1f2f2c9be734 100644
--- a/doc/doxygen/Makefile
+++ b/doc/doxygen/Makefile
@@ -7,7 +7,7 @@ export STRIP_FROM_INC_PATH_LIST=$(shell \
 
 # use lessc (http://lesscss.org/#using-less) for compiling CSS
 # It can also be installed in ubuntu with the `node-less` package
-LESSC ?= $(shell command -v lessc 2>/dev/null)
+LESSC ?= lessc
 
 DOCUMENTATION_FORMAT ?= html
 
@@ -16,7 +16,7 @@ doc: $(DOCUMENTATION_FORMAT)
 
 # by marking html as phony we force make to re-run Doxygen even if the directory exists.
 .PHONY: html
-html: src/css/riot.css src/changelog.md
+html: src/changelog.md
 	( cat riot.doxyfile ; echo "GENERATE_HTML = yes" ) | doxygen -
 
 .PHONY: check
@@ -27,14 +27,12 @@ check: src/changelog.md
 man: src/changelog.md
 	( cat riot.doxyfile ; echo "GENERATE_MAN = yes" ) | doxygen -
 
-ifneq (,$(LESSC))
 src/css/riot.css: src/css/riot.less src/css/variables.less
 	@$(LESSC) $< $@
 
 src/css/variables.less: src/config.json
 	@grep "^\s*\"@" $< | sed -e 's/^\s*"//g' -e 's/":\s*"/: /g' \
 	  -e 's/",\?$$/;/g' -e 's/\\"/"/g' > $@
-endif
 
 src/changelog.md: src/changelog.md.tmp ../../release-notes.txt
 	@./generate-changelog.py $+ $@