diff --git a/types/vote.go b/types/vote.go
index 30205d884..4fca422d6 100644
--- a/types/vote.go
+++ b/types/vote.go
@@ -54,6 +54,9 @@ func (vote *Vote) Copy() *Vote {
 }
 
 func (vote *Vote) String() string {
+	if vote == nil {
+		return "nil-Vote"
+	}
 	var typeString string
 	switch vote.Type {
 	case VoteTypePrevote: