diff --git a/internal/datacoord/allocator.go b/internal/datacoord/allocator.go
index c868a48f38..6c0b2b8c8f 100644
--- a/internal/datacoord/allocator.go
+++ b/internal/datacoord/allocator.go
@@ -31,6 +31,7 @@ type allocator interface {
 	allocID(context.Context) (UniqueID, error)
 }
 
+// make sure rootCoordAllocator implements allocator interface
 var _ allocator = (*rootCoordAllocator)(nil)
 
 // rootCoordAllocator use RootCoord as allocator