diff --git a/ble_darwin.go b/ble_darwin.go
index 3196788..ed3b210 100644
--- a/ble_darwin.go
+++ b/ble_darwin.go
@@ -165,6 +165,8 @@ type DiscoverCharacteristicEvent struct {
 }
 
 type UpdateValueEvent struct {
+	Peripheral Peripheral
+	Characteristic *ns.CBCharacteristic
 	Data []byte
 }
 
@@ -247,6 +249,9 @@ func (b *BLE) StopScan() {
 
 func CancelConnection(p Peripheral) {
 	b := pdLookup[p.p.Ptr()]
+	if b == nil {
+		return
+	}
 	b.connections.Lock()
 	var ch chan string;
 	for _, item := range b.connections.items {
@@ -494,6 +499,8 @@ func updateValue(p *ns.CBPeripheral, chr *ns.CBCharacteristic, e *ns.NSError) {
 	b := pdLookup[p.Ptr()]
 	v := chr.Value()
 	b.events <-UpdateValueEvent{
+		Peripheral: newPeripheral(p),
+		Characteristic: chr,
 		Data: C.GoBytes(v.Bytes(), (C.int)(v.Length())),
 	}
 }