diff --git a/Extensions/FreeSql.Extensions.JsonMap/FreeSql.Extensions.JsonMap.zip b/Extensions/FreeSql.Extensions.JsonMap/FreeSql.Extensions.JsonMap.zip
new file mode 100644
index 00000000..bfdb67b2
Binary files /dev/null and b/Extensions/FreeSql.Extensions.JsonMap/FreeSql.Extensions.JsonMap.zip differ
diff --git a/FreeSql/Internal/UtilsExpressionTree.cs b/FreeSql/Internal/UtilsExpressionTree.cs
index 9e570b04..9b84beed 100644
--- a/FreeSql/Internal/UtilsExpressionTree.cs
+++ b/FreeSql/Internal/UtilsExpressionTree.cs
@@ -187,7 +187,9 @@ namespace FreeSql.Internal
                 }
                 try
                 {
-                    col.DbDefaultValue = common.GetNoneParamaterSqlValue(new List<DbParameter>(), "init", col, colattr.MapType, defaultValue);
+                    var initParms = new List<DbParameter>();
+                    col.DbDefaultValue = common.GetNoneParamaterSqlValue(initParms, "init", col, colattr.MapType, defaultValue);
+                    if (initParms.Any()) col.DbDefaultValue = "NULL";
                 }
                 catch
                 {