diff --git a/gcc/config.sub b/gcc/config.sub
index e5f8db57ebc3f7871281f8e0a687617ca7a4b9ce..a5095547d17ac3ded231c6c2d984037c495b4d92 100755
--- a/gcc/config.sub
+++ b/gcc/config.sub
@@ -170,7 +170,13 @@ case $basic_machine in
 		;;
 	iris | iris4d)
 		basic_machine=mips-sgi
-		os=-irix
+		case $os in
+		    -irix*)
+			;;
+		    *)
+			os=-irix4
+			;;
+		esac
 		;;
 	news | news700 | news800 | news900)
 		basic_machine=m68k-sony