diff --git a/NewLife.Redis/RedisBase.cs b/NewLife.Redis/RedisBase.cs
index ab546b3..b25c504 100644
--- a/NewLife.Redis/RedisBase.cs
+++ b/NewLife.Redis/RedisBase.cs
@@ -79,7 +79,8 @@ protected virtual Packet ToBytes(Object value)
         if (type == typeof(Byte[])) return pk.ToArray();
         if (type.As<IAccessor>()) return type.AccessorRead(pk);
 
-        var str = pk.ToStr().Trim('\"');
+        var str = pk.ToStr() ?? "";
+        str = str.Trim('\"');
         if (type.GetTypeCode() == TypeCode.String) return str;
         if (type.GetTypeCode() != TypeCode.Object) return str.ChangeType(type);