diff --git a/consensus/state.go b/consensus/state.go
index b5fb1c0d1..acb001063 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -1492,7 +1492,7 @@ func (cs *State) recordMetrics(height int64, block *types.Block) {
 					"validator_address", privValAddress.String(),
 				}
 				cs.metrics.ValidatorPower.With(label...).Set(float64(val.VotingPower))
-				if !commitSig.Absent() {
+				if commitSig.ForBlock() {
 					cs.metrics.ValidatorLastSignedHeight.With(label...).Set(float64(height))
 				} else {
 					cs.metrics.ValidatorMissedBlocks.With(label...).Add(float64(1))
diff --git a/types/block.go b/types/block.go
index 45cb8d827..206ea4414 100644
--- a/types/block.go
+++ b/types/block.go
@@ -466,6 +466,11 @@ func NewCommitSigForBlock(signature []byte, valAddr Address, ts time.Time) Commi
 	}
 }
 
+// ForBlock returns true if CommitSig is for the block.
+func (cs CommitSig) ForBlock() bool {
+	return cs.BlockIDFlag == BlockIDFlagCommit
+}
+
 // NewCommitSigAbsent returns new CommitSig with BlockIDFlagAbsent. Other
 // fields are all empty.
 func NewCommitSigAbsent() CommitSig {