diff --git a/chain/events/events_height.go b/chain/events/events_height.go
index c8dd905d9b1..1fcff9e68f1 100644
--- a/chain/events/events_height.go
+++ b/chain/events/events_height.go
@@ -153,6 +153,7 @@ func (e *heightEvents) ChainAt(hnd HeightHandler, rev RevertHandler, confidence
 
 	best, err := e.tsc.best()
 	if err != nil {
+		e.lk.Unlock()
 		return xerrors.Errorf("error getting best tipset: %w", err)
 	}
 
@@ -177,6 +178,7 @@ func (e *heightEvents) ChainAt(hnd HeightHandler, rev RevertHandler, confidence
 		e.lk.Lock()
 		best, err = e.tsc.best()
 		if err != nil {
+			e.lk.Unlock()
 			return xerrors.Errorf("error getting best tipset: %w", err)
 		}
 		bestH = best.Height()