diff --git a/pkg/logutil/zap_journald.go b/pkg/logutil/zap_journald.go
index affef6418..9999eb796 100644
--- a/pkg/logutil/zap_journald.go
+++ b/pkg/logutil/zap_journald.go
@@ -41,6 +41,8 @@ type journaldWriter struct {
 	io.Writer
 }
 
+// WARN: assume that etcd uses default field names in zap encoder config
+// make sure to keep this up-to-date!
 type logLine struct {
 	Level  string `json:"level"`
 	Caller string `json:"caller"`