diff --git a/mysql-test/main/func_time.result b/mysql-test/main/func_time.result
index 4f7000be7b2..151dbc8d5d8 100644
--- a/mysql-test/main/func_time.result
+++ b/mysql-test/main/func_time.result
@@ -3511,3 +3511,29 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1003	select TIMESTAMP'2001-01-01 10:20:30' + interval '10' year AS `c1`,TIMESTAMP'2001-01-01 10:20:30' + interval '10' year AS `c2`,TIMESTAMP'2001-01-01 10:20:30' + interval '10' year AS `c3`
+CREATE TABLE t_ts   (a timestamp(6));
+CREATE TABLE t_trig (a timestamp(6));
+CREATE FUNCTION fn_sleep_before_now() returns int
+BEGIN
+INSERT INTO t_ts SET a= current_timestamp(6);
+RETURN 0;
+END//
+CREATE TRIGGER trg_insert_t_ts after INSERT on t_ts for each row
+BEGIN
+INSERT into t_trig set a= current_timestamp(6);
+END//
+SET @sav_slow_query_log= @@session.slow_query_log;
+SET @@session.slow_query_log= ON;
+SELECT current_timestamp(6),fn_sleep_before_now() INTO @ts_cur, @ts_func;
+SELECT a FROM t_ts   LIMIT 1 into @ts_func;
+SELECT a FROM t_trig LIMIT 1 into @ts_trig;
+DELETE FROM t_ts;
+DELETE FROM t_trig;
+SET @@session.slow_query_log= OFF;
+SELECT current_timestamp(6),fn_sleep_before_now() INTO @ts_cur, @func_ts;
+SELECT a FROM t_ts   LIMIT 1 into @ts_func;
+SELECT a FROM t_trig LIMIT 1 into @ts_trig;
+SET @@session.slow_query_log= @sav_slow_query_log;
+DROP FUNCTION fn_sleep_before_now;
+DROP TRIGGER trg_insert_t_ts;
+DROP TABLE t_ts, t_trig;
diff --git a/mysql-test/main/func_time.test b/mysql-test/main/func_time.test
index b3a114a7a03..ecbf23f8e36 100644
--- a/mysql-test/main/func_time.test
+++ b/mysql-test/main/func_time.test
@@ -2077,3 +2077,61 @@ EXPLAIN EXTENDED SELECT
   TIMESTAMP'2001-01-01 10:20:30' + INTERVAL '10' YEAR AS c1,
   INTERVAL '10' YEAR + TIMESTAMP'2001-01-01 10:20:30' AS c2,
   +INTERVAL '10' YEAR + TIMESTAMP'2001-01-01 10:20:30' AS c3;
+
+############
+# MDEV-13727
+# Current timestamp functions inside stored functions must return the
+# value of the top-level statement's timestamp (its start time).
+# This must hold regardless of @@slow_query_log option.
+#
+
+CREATE TABLE t_ts   (a timestamp(6));
+CREATE TABLE t_trig (a timestamp(6));
+delimiter //;
+CREATE FUNCTION fn_sleep_before_now() returns int
+BEGIN
+  INSERT INTO t_ts SET a= current_timestamp(6);
+  RETURN 0;
+END//
+CREATE TRIGGER trg_insert_t_ts after INSERT on t_ts for each row
+BEGIN
+  INSERT into t_trig set a= current_timestamp(6);
+END//
+delimiter ;//
+
+SET @sav_slow_query_log= @@session.slow_query_log;
+
+# @@slow_query_log ON check
+SET @@session.slow_query_log= ON;
+SELECT current_timestamp(6),fn_sleep_before_now() INTO @ts_cur, @ts_func;
+
+SELECT a FROM t_ts   LIMIT 1 into @ts_func;
+SELECT a FROM t_trig LIMIT 1 into @ts_trig;
+if (!`SELECT @ts_cur = @ts_func and @ts_func = @ts_trig`)
+{
+  SELECT @ts_cur, @ts_func, @ts_trig;
+  --die Error: timestamps must be equal but they diverge
+}
+DELETE FROM t_ts;
+DELETE FROM t_trig;
+
+# @@slow_query_log OFF check
+SET @@session.slow_query_log= OFF;
+SELECT current_timestamp(6),fn_sleep_before_now() INTO @ts_cur, @func_ts;
+SELECT a FROM t_ts   LIMIT 1 into @ts_func;
+SELECT a FROM t_trig LIMIT 1 into @ts_trig;
+if (!`SELECT @ts_cur = @ts_func and @ts_func = @ts_trig`)
+{
+  SELECT @ts_cur, @ts_func, @ts_trig;
+  --die Error: timestamps must be equal but they diverge
+}
+
+# Cleanup
+SET @@session.slow_query_log= @sav_slow_query_log;
+DROP FUNCTION fn_sleep_before_now;
+DROP TRIGGER trg_insert_t_ts;
+DROP TABLE t_ts, t_trig;
+
+#
+# End of MDEV-13727
+###################
diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index ba682beb9c8..3ec234759e3 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -3473,7 +3473,6 @@ sp_instr_stmt::execute(THD *thd, uint *nextp)
   int res;
   bool save_enable_slow_log;
   const CSET_STRING query_backup= thd->query_string;
-  QUERY_START_TIME_INFO time_info;
   Sub_statement_state backup_state;
   DBUG_ENTER("sp_instr_stmt::execute");
   DBUG_PRINT("info", ("command: %d", m_lex_keeper.sql_command()));
@@ -3483,15 +3482,7 @@ sp_instr_stmt::execute(THD *thd, uint *nextp)
   thd->profiling.set_query_source(m_query.str, m_query.length);
 #endif
 
-  if ((save_enable_slow_log= thd->enable_slow_log))
-  {
-    /*
-      Save start time info for the CALL statement and overwrite it with the
-      current time for log_slow_statement() to log the individual query timing.
-    */
-    thd->backup_query_start_time(&time_info);
-    thd->set_time();
-  }
+  save_enable_slow_log= thd->enable_slow_log;
   thd->store_slow_query_state(&backup_state);
 
   if (!(res= alloc_query(thd, m_query.str, m_query.length)) &&
@@ -3555,9 +3546,6 @@ sp_instr_stmt::execute(THD *thd, uint *nextp)
       thd->get_stmt_da()->reset_diagnostics_area();
     }
   }
-  /* Restore the original query start time */
-  if (thd->enable_slow_log)
-    thd->restore_query_start_time(&time_info);
 
   DBUG_RETURN(res || thd->is_error());
 }
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 37e4697e708..03e4660d8ef 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -2139,26 +2139,6 @@ struct wait_for_commit
   void reinit();
 };
 
-/*
-  Structure to store the start time for a query
-*/
-
-struct QUERY_START_TIME_INFO
-{
-  my_time_t start_time;
-  ulong     start_time_sec_part;
-  ulonglong start_utime, utime_after_lock;
-
-  void backup_query_start_time(QUERY_START_TIME_INFO *backup)
-  {
-    *backup= *this;
-  }
-  void restore_query_start_time(QUERY_START_TIME_INFO *backup)
-  {
-    *this= *backup;
-  }
-};
-
 extern "C" void my_message_sql(uint error, const char *str, myf MyFlags);
 
 /**
@@ -2177,8 +2157,7 @@ class THD :public Statement,
            */
            public Item_change_list,
            public MDL_context_owner,
-           public Open_tables_state,
-           public QUERY_START_TIME_INFO
+           public Open_tables_state
 {
 private:
   inline bool is_stmt_prepare() const
@@ -2403,10 +2382,12 @@ public:
   uint32     file_id;			// for LOAD DATA INFILE
   /* remote (peer) port */
   uint16     peer_port;
+  my_time_t  start_time;             // start_time and its sec_part 
+  ulong      start_time_sec_part;    // are almost always used separately
   my_hrtime_t user_time;
   // track down slow pthread_create
   ulonglong  prior_thr_create_utime, thr_create_utime;
-  ulonglong  utime_after_query;
+  ulonglong  start_utime, utime_after_lock, utime_after_query;
 
   // Process indicator
   struct {