diff --git a/storage/storagepb/kv.pb.go b/storage/storagepb/kv.pb.go
index 92835c6c5..b293db81a 100644
--- a/storage/storagepb/kv.pb.go
+++ b/storage/storagepb/kv.pb.go
@@ -74,9 +74,9 @@ func (*KeyValue) ProtoMessage()    {}
 
 type Event struct {
 	Type Event_EventType `protobuf:"varint,1,opt,name=type,proto3,enum=storagepb.Event_EventType" json:"type,omitempty"`
-	// a put event contains the current key-value
-	// a delete/expire event contains the previous
-	// key-value
+	// A PUT event contains current kv pair.
+	// A PUT event with kv.Version=1 indicates the creation of a key.
+	// A DELETE/EXPIRE event contains previous kv pair
 	Kv *KeyValue `protobuf:"bytes,2,opt,name=kv" json:"kv,omitempty"`
 }
 
diff --git a/storage/storagepb/kv.proto b/storage/storagepb/kv.proto
index ba8820542..6ccde1d06 100644
--- a/storage/storagepb/kv.proto
+++ b/storage/storagepb/kv.proto
@@ -32,8 +32,8 @@ message Event {
     EXPIRE = 2;
   }
   EventType type = 1;
-  // a put event contains the current key-value
-  // a delete/expire event contains the previous
-  // key-value
+  // A PUT event contains current kv pair.
+  // A PUT event with kv.Version=1 indicates the creation of a key.
+  // A DELETE/EXPIRE event contains previous kv pair
   KeyValue kv = 2;
 }