diff --git a/src/main/java/org/ntlab/amaryllis/server/entities/Voicememo.java b/src/main/java/org/ntlab/amaryllis/server/entities/Voicememo.java
index 80ad11c..c079c08 100644
--- a/src/main/java/org/ntlab/amaryllis/server/entities/Voicememo.java
+++ b/src/main/java/org/ntlab/amaryllis/server/entities/Voicememo.java
@@ -16,9 +16,9 @@
     private String summary;
     private Integer times;
     @JsonIgnore
-    private ArrayList<String> favolist;
+    private ArrayList<String> favolist = new ArrayList<>();
     private Integer favos;
-    private ArrayList<String> categories;
+    private ArrayList<String> categories = new ArrayList<>();
     private HashMap<String,Comment> commentMap = new HashMap<>();
 
     public Voicememo(String vid, String uid, Integer time, String url, double latitude, double longitude, String title, String summary) {