diff --git a/Src/Asp.NetCore2/SqlSugar/SqlSugarClient.cs b/Src/Asp.NetCore2/SqlSugar/SqlSugarClient.cs
index 4bcaf2207..9ca204ade 100644
--- a/Src/Asp.NetCore2/SqlSugar/SqlSugarClient.cs
+++ b/Src/Asp.NetCore2/SqlSugar/SqlSugarClient.cs
@@ -925,6 +925,10 @@ namespace SqlSugar
                 db.Context.Ado.BeginTran();
             }
             db.Context.Root = this;
+            if (db.Context.MappingTables == null) 
+            {
+                db.Context.MappingTables = new MappingTableList();
+            }
             return db.Context;
         }