diff --git a/formatter_keyvalue.go b/formatter_keyvalue.go
index 3beb441..e823143 100644
--- a/formatter_keyvalue.go
+++ b/formatter_keyvalue.go
@@ -35,6 +35,7 @@ func NewFormatterKeyValue() *FormatterKeyValue {
 func (formatter *FormatterKeyValue) Begin(entry *Entry) {
 	// reset builder
 	formatter.builder.Reset()
+	formatter.isFirstKVWritten = false
 
 	// add timestamp
 	formatter.addKV("time", entry.Time.Format(formatter.TimeFormat))