diff --git a/sql/rpl_parallel.cc b/sql/rpl_parallel.cc
index d9ff07fa740..ac96d92eb5d 100644
--- a/sql/rpl_parallel.cc
+++ b/sql/rpl_parallel.cc
@@ -2538,8 +2538,10 @@ rpl_parallel::stop_during_until()
 bool
 rpl_parallel::workers_idle(Relay_log_info *rli)
 {
-  return rli->last_inuse_relaylog->queued_count ==
-         rli->last_inuse_relaylog->dequeued_count;
+  mysql_mutex_assert_owner(&rli->data_lock);
+  return !rli->last_inuse_relaylog ||
+    rli->last_inuse_relaylog->queued_count ==
+    rli->last_inuse_relaylog->dequeued_count;
 }
 
 
diff --git a/sql/slave.cc b/sql/slave.cc
index 2cc11b9ed42..f4d76e447cd 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -5369,19 +5369,25 @@ pthread_handler_t handle_slave_sql(void *arg)
   }
   else
     rli->gtid_skip_flag = GTID_SKIP_NOT;
+  mysql_mutex_lock(&rli->data_lock);
   if (init_relay_log_pos(rli,
                          rli->group_relay_log_name,
                          rli->group_relay_log_pos,
-                         1 /*need data lock*/, &errmsg,
+                         0 /*need data lock*/, &errmsg,
                          1 /*look for a description_event*/))
   { 
     rli->report(ERROR_LEVEL, ER_SLAVE_FATAL_ERROR, NULL,
                 "Error initializing relay log position: %s", errmsg);
+    mysql_mutex_unlock(&rli->data_lock);
     goto err_before_start;
   }
   rli->reset_inuse_relaylog();
   if (rli->alloc_inuse_relaylog(rli->group_relay_log_name))
+  {
+    mysql_mutex_unlock(&rli->data_lock);
     goto err_before_start;
+  }
+  mysql_mutex_unlock(&rli->data_lock);
 
   strcpy(rli->future_event_master_log_name, rli->group_master_log_name);
   THD_CHECK_SENTRY(thd);