diff --git a/sync.go b/sync.go
index 9334a293..a7453bec 100644
--- a/sync.go
+++ b/sync.go
@@ -110,6 +110,7 @@ type DefaultSyncer struct {
 }
 
 var _ Syncer = (*DefaultSyncer)(nil)
+var _ ExtensibleSyncer = (*DefaultSyncer)(nil)
 
 // NewDefaultSyncer returns an instantiated DefaultSyncer
 func NewDefaultSyncer() *DefaultSyncer {