diff --git a/states.go b/states.go
index 6d7f2822b..d2d06a7ca 100644
--- a/states.go
+++ b/states.go
@@ -187,7 +187,7 @@ func (m *Sealing) handleCommitting(ctx statemachine.Context, sector SectorInfo)
 
 	params := &miner.ProveCommitSectorParams{
 		SectorNumber: sector.SectorID,
-		Proof:        abi.SealProof{ProofBytes: proof},
+		Proof:        proof,
 	}
 
 	enc, aerr := actors.SerializeParams(params)