diff --git a/services/syncbase/bridge/cgo/impl.go b/services/syncbase/bridge/cgo/impl.go
index a0788e8..ce14e19 100644
--- a/services/syncbase/bridge/cgo/impl.go
+++ b/services/syncbase/bridge/cgo/impl.go
@@ -46,7 +46,7 @@
 	"v.io/v23/vom"
 	_ "v.io/x/ref/runtime/factories/roaming"
 	"v.io/x/ref/services/syncbase/bridge"
-	"v.io/x/ref/services/syncbase/bridge/cgo/refmap"
+	"v.io/x/ref/services/syncbase/bridge/cgo/ptrmap"
 	"v.io/x/ref/services/syncbase/discovery"
 	"v.io/x/ref/services/syncbase/syncbaselib"
 	"v.io/x/ref/test/testutil"
@@ -96,7 +96,7 @@
 	neighborhoodAdStatus *adStatus
 )
 
-var globalRefMap = refmap.NewRefMap()
+var globalPtrMap = ptrmap.New()
 
 // TODO(razvanm): Replace the function arguments with an options struct.
 //export v23_syncbase_Init
@@ -342,7 +342,7 @@
 }
 
 //export v23_syncbase_NeighborhoodNewScan
-func v23_syncbase_NeighborhoodNewScan(cbs C.v23_syncbase_NeighborhoodScanCallbacks, cUint64 *C.uint64_t, cErr *C.v23_syncbase_VError) {
+func v23_syncbase_NeighborhoodNewScan(cbs C.v23_syncbase_NeighborhoodScanCallbacks, cErr *C.v23_syncbase_VError) {
 	scanCtx, cancel := context.WithCancel(b.Ctx)
 	scanChan := make(chan discovery.AppPeer)
 	err := discovery.ListenForAppPeers(scanCtx, scanChan)
@@ -365,13 +365,15 @@
 	}()
 
 	// Remember the scan's cancellation information and return the scan's id.
-	x := C.uint64_t(globalRefMap.Add(cancel))
-	cUint64 = &x
+	if err := globalPtrMap.Set(uintptr(cbs.handle), cancel); err != nil {
+		cancel()
+		cErr.init(err)
+	}
 }
 
 //export v23_syncbase_NeighborhoodStopScan
-func v23_syncbase_NeighborhoodStopScan(cUint64 C.uint64_t) {
-	if cancel, ok := globalRefMap.Remove(uint64(cUint64)).(context.CancelFunc); ok && cancel != nil {
+func v23_syncbase_NeighborhoodStopScan(cHandle C.v23_syncbase_Handle) {
+	if cancel, ok := globalPtrMap.Remove(uintptr(cHandle)).(context.CancelFunc); ok && cancel != nil {
 		cancel()
 	}
 }
@@ -743,7 +745,7 @@
 // Syncgroup Invites
 
 //export v23_syncbase_DbSyncgroupInvitesNewScan
-func v23_syncbase_DbSyncgroupInvitesNewScan(cName C.v23_syncbase_String, cbs C.v23_syncbase_DbSyncgroupInvitesCallbacks, cUint64 *C.uint64_t, cErr *C.v23_syncbase_VError) {
+func v23_syncbase_DbSyncgroupInvitesNewScan(cName C.v23_syncbase_String, cbs C.v23_syncbase_DbSyncgroupInvitesCallbacks, cErr *C.v23_syncbase_VError) {
 	encodedId := cName.extract()
 	dbId, err := util.DecodeId(encodedId)
 	if err != nil {
@@ -772,14 +774,16 @@
 		}
 	}()
 
-	// Remember the scan's cancellation information and return the scan's id.
-	x := C.uint64_t(globalRefMap.Add(cancel))
-	cUint64 = &x
+	// Remember the scan's cancellation information.
+	if err := globalPtrMap.Set(uintptr(cbs.handle), cancel); err != nil {
+		cancel()
+		cErr.init(err)
+	}
 }
 
 //export v23_syncbase_DbSyncgroupInvitesStopScan
-func v23_syncbase_DbSyncgroupInvitesStopScan(cUint64 C.uint64_t) {
-	if cancel, ok := globalRefMap.Remove(uint64(cUint64)).(context.CancelFunc); ok && cancel != nil {
+func v23_syncbase_DbSyncgroupInvitesStopScan(cHandle C.v23_syncbase_Handle) {
+	if cancel, ok := globalPtrMap.Remove(uintptr(cHandle)).(context.CancelFunc); ok && cancel != nil {
 		cancel()
 	}
 }
diff --git a/services/syncbase/bridge/cgo/jni.go b/services/syncbase/bridge/cgo/jni.go
index 2aed5e7..66a1e69 100644
--- a/services/syncbase/bridge/cgo/jni.go
+++ b/services/syncbase/bridge/cgo/jni.go
@@ -407,7 +407,7 @@
 //export v23_syncbase_internal_onChange
 func v23_syncbase_internal_onChange(handle C.v23_syncbase_Handle, change C.v23_syncbase_WatchChange) {
 	id := uint64(uintptr(handle))
-	h := globalRefMap.Get(id).(*watchPatternsCallbacksHandle)
+	h := globalPtrMap.Get(uintptr(id)).(*watchPatternsCallbacksHandle)
 	env, free := getEnv()
 	obj := change.extractToJava(env)
 	arg := *(*C.jvalue)(unsafe.Pointer(&obj))
@@ -422,7 +422,7 @@
 //export v23_syncbase_internal_onError
 func v23_syncbase_internal_onError(handle C.v23_syncbase_Handle, error C.v23_syncbase_VError) {
 	id := uint64(uintptr(handle))
-	h := globalRefMap.Remove(id).(*watchPatternsCallbacksHandle)
+	h := globalPtrMap.Remove(uintptr(id)).(*watchPatternsCallbacksHandle)
 	env, free := getEnv()
 	obj := error.extractToJava(env)
 	arg := *(*C.jvalue)(unsafe.Pointer(&obj))
@@ -445,11 +445,16 @@
 	cName := newVStringFromJava(env, name)
 	cResumeMarker := newVBytesFromJava(env, resumeMaker)
 	cPatterns := newVCollectionRowPatternsFromJava(env, patterns)
+	ptr := uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks)))
 	cbs := C.newVWatchPatternsCallbacks()
-	cbs.handle = C.v23_syncbase_Handle(uintptr(globalRefMap.Add(&watchPatternsCallbacksHandle{
-		obj:       uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks))),
+	callbacksHandle := &watchPatternsCallbacksHandle{
+		obj:       ptr,
 		callbacks: newJWatchPatternsCallbacks(env, callbacks),
-	})))
+	}
+	if err := globalPtrMap.Set(ptr, callbacksHandle); err != nil {
+		panic(err)
+	}
+	cbs.handle = C.v23_syncbase_Handle(ptr)
 	var cErr C.v23_syncbase_VError
 	v23_syncbase_DbWatchPatterns(cName, cResumeMarker, cPatterns, cbs, &cErr)
 	maybeThrowException(env, &cErr)
@@ -458,7 +463,7 @@
 //export v23_syncbase_internal_onInvite
 func v23_syncbase_internal_onInvite(handle C.v23_syncbase_Handle, invite C.v23_syncbase_Invite) {
 	id := uint64(uintptr(handle))
-	h := globalRefMap.Get(id).(*inviteCallbacksHandle)
+	h := globalPtrMap.Get(uintptr(id)).(*inviteCallbacksHandle)
 	env, free := getEnv()
 	obj := invite.extractToJava(env)
 	arg := *(*C.jvalue)(unsafe.Pointer(&obj))
@@ -479,20 +484,25 @@
 func Java_io_v_syncbase_internal_Database_SyncgroupInvitesNewScan(env *C.JNIEnv, cls C.jclass, name C.jstring, callbacks C.jobject) C.jlong {
 	cName := newVStringFromJava(env, name)
 	cbs := C.newVSyncgroupInvitesCallbacks()
-	cbs.handle = C.v23_syncbase_Handle(uintptr(globalRefMap.Add(&inviteCallbacksHandle{
-		obj:       uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks))),
+	scanId := uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks)))
+	callbacksHandle := &inviteCallbacksHandle{
+		obj:       scanId,
 		callbacks: newJSyncgroupInvitesCallbacks(env, callbacks),
-	})))
+	}
+	if err := globalPtrMap.Set(scanId, callbacksHandle); err != nil {
+		panic(err)
+	}
+	cbs.handle = C.v23_syncbase_Handle(uintptr(scanId))
 	var cErr C.v23_syncbase_VError
-	var scanId C.uint64_t
-	v23_syncbase_DbSyncgroupInvitesNewScan(cName, cbs, &scanId, &cErr)
+	v23_syncbase_DbSyncgroupInvitesNewScan(cName, cbs, &cErr)
 	maybeThrowException(env, &cErr)
 	return C.jlong(scanId)
 }
 
 //export Java_io_v_syncbase_internal_Database_SyncgroupInvitesStopScan
 func Java_io_v_syncbase_internal_Database_SyncgroupInvitesStopScan(env *C.JNIEnv, cls C.jclass, scanId C.jlong) {
-	v23_syncbase_DbSyncgroupInvitesStopScan(C.uint64_t(scanId))
+	v23_syncbase_DbSyncgroupInvitesStopScan(C.v23_syncbase_Handle(scanId))
+	globalPtrMap.Remove(uintptr(scanId))
 }
 
 //export Java_io_v_syncbase_internal_Collection_GetPermissions
@@ -562,7 +572,7 @@
 //export v23_syncbase_internal_onKeyValue
 func v23_syncbase_internal_onKeyValue(handle C.v23_syncbase_Handle, keyValue C.v23_syncbase_KeyValue) {
 	id := uint64(uintptr(handle))
-	h := globalRefMap.Get(id).(*scanCallbacksHandle)
+	h := globalPtrMap.Get(uintptr(id)).(*scanCallbacksHandle)
 	env, free := getEnv()
 	obj := keyValue.extractToJava(env)
 	arg := *(*C.jvalue)(unsafe.Pointer(&obj))
@@ -577,7 +587,7 @@
 //export v23_syncbase_internal_onDone
 func v23_syncbase_internal_onDone(handle C.v23_syncbase_Handle, error C.v23_syncbase_VError) {
 	id := uint64(uintptr(handle))
-	h := globalRefMap.Get(id).(*scanCallbacksHandle)
+	h := globalPtrMap.Get(uintptr(id)).(*scanCallbacksHandle)
 	env, free := getEnv()
 	obj := error.extractToJava(env)
 	arg := *(*C.jvalue)(unsafe.Pointer(&obj))
@@ -588,7 +598,7 @@
 	}
 	C.DeleteGlobalRef(env, unsafe.Pointer(h.obj))
 	free()
-	globalRefMap.Remove(id)
+	globalPtrMap.Remove(uintptr(id))
 }
 
 type scanCallbacksHandle struct {
@@ -602,11 +612,16 @@
 	cHandle := newVStringFromJava(env, handle)
 	cStart := newVBytesFromJava(env, start)
 	cLimit := newVBytesFromJava(env, limit)
-	cbs := C.newVScanCallbacks()
-	cbs.handle = C.v23_syncbase_Handle(uintptr(globalRefMap.Add(&scanCallbacksHandle{
-		obj:       uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks))),
+	ptr := uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks)))
+	callbacksHandle := &scanCallbacksHandle{
+		obj:       ptr,
 		callbacks: newJScanCallbacks(env, callbacks),
-	})))
+	}
+	if err := globalPtrMap.Set(ptr, callbacksHandle); err != nil {
+		panic(err)
+	}
+	cbs := C.newVScanCallbacks()
+	cbs.handle = C.v23_syncbase_Handle(ptr)
 	var cErr C.v23_syncbase_VError
 	v23_syncbase_CollectionScan(cName, cHandle, cStart, cLimit, cbs, &cErr)
 	maybeThrowException(env, &cErr)
@@ -635,7 +650,7 @@
 //export v23_syncbase_internal_onPeer
 func v23_syncbase_internal_onPeer(handle C.v23_syncbase_Handle, peer C.v23_syncbase_AppPeer) {
 	id := uint64(uintptr(handle))
-	h := globalRefMap.Get(id).(*peerCallbacksHandle)
+	h := globalPtrMap.Get(uintptr(id)).(*peerCallbacksHandle)
 	env, free := getEnv()
 	obj := peer.extractToJava(env)
 	arg := *(*C.jvalue)(unsafe.Pointer(&obj))
@@ -655,20 +670,25 @@
 //export Java_io_v_syncbase_internal_Neighborhood_NewScan
 func Java_io_v_syncbase_internal_Neighborhood_NewScan(env *C.JNIEnv, cls C.jclass, callbacks C.jobject) C.jlong {
 	cbs := C.newVNeighborhoodScanCallbacks()
-	cbs.handle = C.v23_syncbase_Handle(uintptr(globalRefMap.Add(&peerCallbacksHandle{
-		obj:       uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks))),
+	scanId := uintptr(unsafe.Pointer(C.NewGlobalRef(env, callbacks)))
+	callbacksHandle := &peerCallbacksHandle{
+		obj:       scanId,
 		callbacks: newJNeigbhorhoodScanCallbacks(env, callbacks),
-	})))
+	}
+	if err := globalPtrMap.Set(scanId, callbacksHandle); err != nil {
+		panic(err)
+	}
+	cbs.handle = C.v23_syncbase_Handle(uintptr(scanId))
 	var cErr C.v23_syncbase_VError
-	var scanId C.uint64_t
-	v23_syncbase_NeighborhoodNewScan(cbs, &scanId, &cErr)
+	v23_syncbase_NeighborhoodNewScan(cbs, &cErr)
 	maybeThrowException(env, &cErr)
 	return C.jlong(scanId)
 }
 
 //export Java_io_v_syncbase_internal_Neighborhood_StopScan
 func Java_io_v_syncbase_internal_Neighborhood_StopScan(env *C.JNIEnv, cls C.jclass, scanId C.jlong) {
-	v23_syncbase_NeighborhoodStopScan(C.uint64_t(scanId))
+	v23_syncbase_NeighborhoodStopScan(C.v23_syncbase_Handle(scanId))
+	globalPtrMap.Remove(uintptr(scanId))
 }
 
 //export Java_io_v_syncbase_internal_Row_Exists
diff --git a/services/syncbase/bridge/cgo/ptrmap/ptrmap.go b/services/syncbase/bridge/cgo/ptrmap/ptrmap.go
new file mode 100644
index 0000000..e250347
--- /dev/null
+++ b/services/syncbase/bridge/cgo/ptrmap/ptrmap.go
@@ -0,0 +1,47 @@
+// Copyright 2015 The Vanadium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ptrmap
+
+import (
+	"fmt"
+	"sync"
+)
+
+func New() *ptrMap {
+	return &ptrMap{
+		refs: make(map[uintptr]interface{}),
+	}
+}
+
+type ptrMap struct {
+	refs map[uintptr]interface{}
+	lock sync.Mutex
+}
+
+func (r *ptrMap) Set(ptr uintptr, val interface{}) error {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	if _, ok := r.refs[ptr]; ok {
+		return fmt.Errorf("already have existing value at address %v", ptr)
+	}
+	r.refs[ptr] = val
+	return nil
+}
+
+func (r *ptrMap) Get(ptr uintptr) interface{} {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	return r.refs[ptr]
+}
+
+func (r *ptrMap) Remove(ptr uintptr) interface{} {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+	val, ok := r.refs[ptr]
+	if ok {
+		delete(r.refs, ptr)
+	}
+	return val
+}
diff --git a/services/syncbase/bridge/cgo/refmap/refmap.go b/services/syncbase/bridge/cgo/refmap/refmap.go
deleted file mode 100644
index a3ab087..0000000
--- a/services/syncbase/bridge/cgo/refmap/refmap.go
+++ /dev/null
@@ -1,49 +0,0 @@
-// Copyright 2016 The Vanadium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package refmap
-
-import (
-	"sync"
-)
-
-func NewRefMap() *refMap {
-	return &refMap{
-		refs: make(map[uint64]interface{}),
-	}
-}
-
-type refMap struct {
-	refs   map[uint64]interface{}
-	lastId uint64
-	lock   sync.Mutex
-}
-
-func (r *refMap) Add(val interface{}) uint64 {
-	r.lock.Lock()
-	defer r.lock.Unlock()
-	id := r.lastId
-	r.lastId++
-	r.refs[id] = val
-	return id
-}
-
-func (r *refMap) Get(id uint64) interface{} {
-	r.lock.Lock()
-	defer r.lock.Unlock()
-	if val, ok := r.refs[id]; ok {
-		return val
-	}
-	return nil
-}
-
-func (r *refMap) Remove(id uint64) interface{} {
-	r.lock.Lock()
-	defer r.lock.Unlock()
-	if val, ok := r.refs[id]; ok {
-		delete(r.refs, id)
-		return val
-	}
-	return nil
-}