diff --git a/rpio.go b/rpio.go
index ea3962b..3ff8997 100644
--- a/rpio.go
+++ b/rpio.go
@@ -705,9 +705,9 @@ func Open() (err error) {
 	var file *os.File
 
 	// Open fd for rw mem access; try dev/mem first (need root)
-	file, err = os.OpenFile("/dev/mem", os.O_RDWR|os.O_SYNC, 0)
+	file, err = os.OpenFile("/dev/mem", os.O_RDWR|os.O_SYNC, os.ModePerm)
 	if os.IsPermission(err) { // try gpiomem otherwise (some extra functions like clock and pwm setting wont work)
-		file, err = os.OpenFile("/dev/gpiomem", os.O_RDWR|os.O_SYNC, 0)
+		file, err = os.OpenFile("/dev/gpiomem", os.O_RDWR|os.O_SYNC, os.ModePerm)
 	}
 	if err != nil {
 		return