diff --git a/makefiles/Makefile.doc.mk b/makefiles/Makefile.doc.mk
index f0ffe94abc..b38d845db9 100644
--- a/makefiles/Makefile.doc.mk
+++ b/makefiles/Makefile.doc.mk
@@ -6,5 +6,5 @@ ifeq ($(PLATFORM), MACOSX)
 endif
 
 refman:
-        cd documentations/doxygen
-        $(DOXYGEN) or-tools.doxy
+	cd documentations/doxygen
+	$(DOXYGEN) or-tools.doxy