diff --git a/mysql-test/suite/innodb/r/purge_pessimistic.result b/mysql-test/suite/innodb/r/purge_pessimistic.result
index a7ce4e13d6009..7ff69724554fa 100644
--- a/mysql-test/suite/innodb/r/purge_pessimistic.result
+++ b/mysql-test/suite/innodb/r/purge_pessimistic.result
@@ -34,3 +34,21 @@ col1
 DROP TABLE t2;
 SET @@GLOBAL.debug_dbug = @old_debug_dbug;
 SET DEBUG_SYNC='RESET';
+#
+#  MDEV-39706  Assertion `!thd || !coordinator_thd' failed
+#
+CREATE TABLE t1(f1 INT NOT NULL)ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1);
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+connect con1,localhost,root,,;
+UPDATE t1 set f1= f1 + 1;
+DELETE FROM t1;
+connection default;
+disconnect con1;
+COMMIT;
+SET @old_view_update= @@global.innodb_trx_purge_view_update_only_debug;
+SET @@GLOBAL.innodb_trx_purge_view_update_only_debug=1;
+SET STATEMENT max_statement_time=0.1 FOR SET GLOBAL innodb_max_purge_lag_wait=1;
+SET @@GLOBAL.innodb_trx_purge_view_update_only_debug=@old_view_update;
+InnoDB		0 transactions not purged
+DROP TABLE t1;
diff --git a/mysql-test/suite/innodb/t/purge_pessimistic.test b/mysql-test/suite/innodb/t/purge_pessimistic.test
index 88be65a6be5fa..83c5f2d4e6c65 100644
--- a/mysql-test/suite/innodb/t/purge_pessimistic.test
+++ b/mysql-test/suite/innodb/t/purge_pessimistic.test
@@ -49,3 +49,24 @@ DROP TABLE t2;
 
 SET @@GLOBAL.debug_dbug = @old_debug_dbug;
 SET DEBUG_SYNC='RESET';
+
+--echo #
+--echo #  MDEV-39706  Assertion `!thd || !coordinator_thd' failed
+--echo #
+CREATE TABLE t1(f1 INT NOT NULL)ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1);
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+
+connect(con1,localhost,root,,);
+UPDATE t1 set f1= f1 + 1;
+DELETE FROM t1;
+
+connection default;
+disconnect con1;
+COMMIT;
+SET @old_view_update= @@global.innodb_trx_purge_view_update_only_debug;
+SET @@GLOBAL.innodb_trx_purge_view_update_only_debug=1;
+SET STATEMENT max_statement_time=0.1 FOR SET GLOBAL innodb_max_purge_lag_wait=1;
+SET @@GLOBAL.innodb_trx_purge_view_update_only_debug=@old_view_update;
+--source include/wait_all_purged.inc
+DROP TABLE t1;
diff --git a/storage/innobase/include/trx0purge.h b/storage/innobase/include/trx0purge.h
index 25b76c0ecccaf..49c5ddfb276e1 100644
--- a/storage/innobase/include/trx0purge.h
+++ b/storage/innobase/include/trx0purge.h
@@ -506,6 +506,14 @@ class purge_sys_t
 
   /** Reset the state of a purge_worker_task at the end of a batch */
   inline void reset_worker_thd(THD *thd) const noexcept;
+
+#ifdef UNIV_DEBUG
+  int reset_coordinator() noexcept
+  {
+    coordinator_thd= nullptr;
+    return 0;
+  }
+#endif /* UNIV_DEBUG */
 };
 
 /** The global data structure coordinating a purge */
diff --git a/storage/innobase/trx/trx0purge.cc b/storage/innobase/trx/trx0purge.cc
index 3614d792578ba..2d5745bc33a52 100644
--- a/storage/innobase/trx/trx0purge.cc
+++ b/storage/innobase/trx/trx0purge.cc
@@ -1472,7 +1472,10 @@ TRANSACTIONAL_TARGET ulint trx_purge(ulint n_tasks, ulint history_size)
 
   purge_sys.clone_oldest_view(thd);
 
-  ut_d(if (srv_purge_view_update_only_debug) return 0);
+#ifdef UNIV_DEBUG
+  if (srv_purge_view_update_only_debug)
+    return purge_sys.reset_coordinator();
+#endif /* UNIV_DEBUG */
 
   /* Fetch the UNDO recs that need to be purged. */
   ulint n_work= 0;