diff --git a/build/forks.go b/build/forks.go
new file mode 100644
index 000000000..2aa1e8509
--- /dev/null
+++ b/build/forks.go
@@ -0,0 +1,3 @@
+package build
+
+const ForkCCM = 1700
diff --git a/chain/sync.go b/chain/sync.go
index 0015462bd..22f39eb8c 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -513,9 +513,13 @@ 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")
+		// FORK START
+		if h.Height > build.ForkCCM {
+			if len(h.EPostProof.Candidates) == 0 {
+				return xerrors.Errorf("no candidates")
+			}
 		}
+		// FORK END
 
 		for _, t := range h.EPostProof.Candidates {
 			if !types.IsTicketWinner(t.Partial, ssize, snum.Uint64(), tpow) {