diff --git a/docs/GNUmakefile b/docs/GNUmakefile
index 9f498cf..6e32474 100644
--- a/docs/GNUmakefile
+++ b/docs/GNUmakefile
@@ -25,5 +25,5 @@ ml-principle2.eps:	ml-principle2.fig
 directory-struct.eps:	directory-struct.fig
 
 clean distclean realclean:
-	rm  petidomo.aux petidomo.dvi petidomo.idx petidomo.log petidomo.ps petidomo.toc
+	rm -f petidomo.aux petidomo.dvi petidomo.idx petidomo.log petidomo.ps petidomo.toc
 	rm -f ml-principle1.eps ml-principle2.eps directory-struct.eps