diff --git a/shell/ash.c b/shell/ash.c
index f9d59e50e..e24b74c03 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -14312,9 +14312,9 @@ procargs(char **argv)
 	}
 	if (mflag == 2)
 		mflag = iflag;
+	/* Unset options which weren't explicitly set or unset */
 	for (i = 0; i < NOPTS; i++)
-		if (optlist[i] == 2)
-			optlist[i] = 0;
+		optlist[i] &= 1; /* same effect as "if (optlist[i] == 2) optlist[i] = 0;" */
 #if DEBUG == 2
 	debug = 1;
 #endif