diff --git a/gap_darwin.go b/gap_darwin.go
index 19b4af8..996abd4 100644
--- a/gap_darwin.go
+++ b/gap_darwin.go
@@ -90,8 +90,7 @@ type Device struct {
 	servicesChan chan error
 	charsChan    chan error
 
-	services        map[UUID]*DeviceService
-	characteristics map[UUID]*DeviceCharacteristic
+	services map[UUID]*DeviceService
 }
 
 // Connect starts a connection attempt to the given peripheral device address.
@@ -159,14 +158,16 @@ func (pd *peripheralDelegate) DidDiscoverCharacteristics(prph cbgo.Peripheral, s
 // for a Peripheral receives a notification with a new value,
 // or receives a value for a read request.
 func (pd *peripheralDelegate) DidUpdateValueForCharacteristic(prph cbgo.Peripheral, chr cbgo.Characteristic, err error) {
+	svcuuid, _ := ParseUUID(chr.Service().UUID().String())
 	uuid, _ := ParseUUID(chr.UUID().String())
-	if char, ok := pd.d.characteristics[uuid]; ok {
-		if err == nil && char.callback != nil {
-			go char.callback(chr.Value())
-		}
-
-		if char.readChan != nil {
-			char.readChan <- err
+	if svc, ok := pd.d.services[svcuuid]; ok {
+		if char, ok := svc.characteristics[uuid]; ok {
+			if err == nil && char.callback != nil {
+				go char.callback(chr.Value())
+			}
+			if char.readChan != nil {
+				char.readChan <- err
+			}
 		}
 	}
 }
diff --git a/gattc_darwin.go b/gattc_darwin.go
index 32876b3..92998ee 100644
--- a/gattc_darwin.go
+++ b/gattc_darwin.go
@@ -14,7 +14,7 @@ import (
 //
 // Passing a nil slice of UUIDs will return a complete list of
 // services.
-func (d *Device) DiscoverServices(uuids []UUID) ([]DeviceService, error) {
+func (d *Device) DiscoverServices(uuids []UUID) ([]*DeviceService, error) {
 	d.prph.DiscoverServices([]cbgo.UUID{})
 
 	// clear cache of services
@@ -23,7 +23,7 @@ func (d *Device) DiscoverServices(uuids []UUID) ([]DeviceService, error) {
 	// wait on channel for service discovery
 	select {
 	case <-d.servicesChan:
-		svcs := []DeviceService{}
+		svcs := []*DeviceService{}
 		for _, dsvc := range d.prph.Services() {
 			dsvcuuid, _ := ParseUUID(dsvc.UUID().String())
 			// add if in our original list
@@ -41,13 +41,13 @@ func (d *Device) DiscoverServices(uuids []UUID) ([]DeviceService, error) {
 				}
 			}
 
-			svc := DeviceService{
+			svc := &DeviceService{
 				uuidWrapper: dsvcuuid,
 				device:      d,
 				service:     dsvc,
 			}
 			svcs = append(svcs, svc)
-			d.services[svc.uuidWrapper] = &svc
+			d.services[svc.uuidWrapper] = svc
 		}
 		return svcs, nil
 	case <-time.NewTimer(10 * time.Second).C:
@@ -65,7 +65,8 @@ type DeviceService struct {
 
 	device *Device
 
-	service cbgo.Service
+	service         cbgo.Service
+	characteristics map[UUID]*DeviceCharacteristic
 }
 
 // UUID returns the UUID for this DeviceService.
@@ -88,7 +89,7 @@ func (s *DeviceService) DiscoverCharacteristics(uuids []UUID) ([]DeviceCharacter
 	s.device.prph.DiscoverCharacteristics(cbuuids, s.service)
 
 	// clear cache of characteristics
-	s.device.characteristics = make(map[UUID]*DeviceCharacteristic)
+	s.characteristics = make(map[UUID]*DeviceCharacteristic)
 
 	// wait on channel for characteristic discovery
 	select {
@@ -119,7 +120,7 @@ func (s *DeviceService) DiscoverCharacteristics(uuids []UUID) ([]DeviceCharacter
 				},
 			}
 			chars = append(chars, char)
-			s.device.characteristics[char.uuidWrapper] = &char
+			s.characteristics[char.uuidWrapper] = &char
 		}
 		return chars, nil
 	case <-time.NewTimer(10 * time.Second).C: