diff --git a/sql/mdl.cc b/sql/mdl.cc
index a883b21423e..6187d4515a3 100644
--- a/sql/mdl.cc
+++ b/sql/mdl.cc
@@ -1254,7 +1254,8 @@ MDL_context::wait_for_locks(MDL_request_list *mdl_requests)
     }
     if (!mdl_request)
     {
-      pthread_mutex_unlock(&LOCK_mdl);
+      /* As a side-effect MDL_EXIT_COND() unlocks LOCK_mdl. */
+      MDL_EXIT_COND(m_thd, mysys_var, old_msg);
       break;
     }
     pthread_cond_wait(&COND_mdl, &LOCK_mdl);
diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 99a0b33f213..61028f692b3 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -3693,6 +3693,7 @@ recover_from_failed_open_table_attempt(THD *thd, TABLE_LIST *table)
     case OT_WAIT:
       result= (thd->mdl_context.wait_for_locks(&m_mdl_requests) ||
                tdc_wait_for_old_versions(thd, &m_mdl_requests));
+      DBUG_ASSERT(thd->mysys_var->current_mutex == NULL);
       break;
     case OT_DISCOVER:
       {