diff --git a/doc/doxygen/Makefile b/doc/doxygen/Makefile
index c64e7d411a..4aa28879ae 100644
--- a/doc/doxygen/Makefile
+++ b/doc/doxygen/Makefile
@@ -1,4 +1,9 @@
-doc:
+.PHONY: doc
+doc: html
+
+# by marking html as phony we force make to re-run Doxygen even if the directory exists.
+.PHONY: html
+html:
 	doxygen riot.doxyfile
 
 clean: