diff --git a/chain/sync.go b/chain/sync.go
index b65341825..0015462bd 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -513,6 +513,10 @@ func (syncer *Syncer) ValidateBlock(ctx context.Context, b *types.FullBlock) err
 
 		snum := types.BigDiv(mpow, types.NewInt(ssize))
 
+		if len(h.EPostProof.Candidates) == 0 {
+			return xerrors.Errorf("no candidates")
+		}
+
 		for _, t := range h.EPostProof.Candidates {
 			if !types.IsTicketWinner(t.Partial, ssize, snum.Uint64(), tpow) {
 				return xerrors.Errorf("miner created a block but was not a winner")