diff --git a/manual/Makefile b/manual/Makefile
index a64394792d..19085e1019 100644
--- a/manual/Makefile
+++ b/manual/Makefile
@@ -60,6 +60,8 @@ format:: test
 
 clean::
 	@rm -rf $(OUTDIR)
+	@for file in `find xml/ -name '*.bak' -type f`; do \
+		rm $$file; done
 
 .PHONY : clean