diff --git a/sql/mdl.h b/sql/mdl.h
index cfa3e671706..e3e41652bf4 100644
--- a/sql/mdl.h
+++ b/sql/mdl.h
@@ -148,8 +148,9 @@ struct I_P_List_adapter
   or destructor for it.
 */
 
-struct MDL_request
+class MDL_request
 {
+public:
   /** Type of metadata lock. */
   enum          enum_mdl_type type;
 
diff --git a/sql/table.h b/sql/table.h
index 02492ea4e81..b6ea372b41e 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -30,8 +30,8 @@ class st_select_lex;
 class partition_info;
 class COND_EQUAL;
 class Security_context;
-struct MDL_request;
-struct MDL_ticket;
+class MDL_request;
+class MDL_ticket;
 
 /*************************************************************************/