diff --git a/mysql-test/suite/rpl/r/mdev38829_semisync_write_fail.result b/mysql-test/suite/rpl/r/mdev38829_semisync_write_fail.result
new file mode 100644
index 0000000000000..f1ffe58f266cb
--- /dev/null
+++ b/mysql-test/suite/rpl/r/mdev38829_semisync_write_fail.result
@@ -0,0 +1,18 @@
+call mtr.add_suppression("Write to binary log failed*");
+SET GLOBAL rpl_semi_sync_master_enabled = 1;
+SET GLOBAL rpl_semi_sync_master_wait_point = 'AFTER_SYNC';
+set @saved_dbug = @@global.debug_dbug;
+SET GLOBAL debug_dbug='d,injecting_fault_writing';
+CREATE TABLE t1 (i INT);
+CREATE TABLE t1 (i INT);
+ERROR HY000: Error writing file 'master-bin' ((errno: #)
+set @@global.debug_dbug = @saved_dbug;
+SELECT 1;
+1
+1
+SHOW STATUS LIKE 'Rpl_semi_sync_master_status';
+Variable_name	Value
+Rpl_semi_sync_master_status	ON
+SET GLOBAL rpl_semi_sync_master_enabled = 0;
+SET GLOBAL rpl_semi_sync_master_wait_point = DEFAULT;
+DROP TABLE IF EXISTS t1;
diff --git a/mysql-test/suite/rpl/t/mdev38829_semisync_write_fail.test b/mysql-test/suite/rpl/t/mdev38829_semisync_write_fail.test
new file mode 100644
index 0000000000000..65cd234012d9c
--- /dev/null
+++ b/mysql-test/suite/rpl/t/mdev38829_semisync_write_fail.test
@@ -0,0 +1,36 @@
+#
+# MDEV-38829: Assertion `rpl_semi_sync_master_off_times >
+# thd->expected_semi_sync_offs' failed in Repl_semi_sync_master::commit_trx()
+#
+# A failed direct binlog write (write_gtid_event()/write_event() returning an
+# error) left semisync registration skipped, but the semisync wait
+# (wait_after_sync() -> commit_trx()) still ran unconditionally. commit_trx()
+# then found no entry for the transaction and asserted that the only
+# possible cause was a concurrent switch_off()/switch_on(), which is false
+# here -- the entry was simply never registered.
+#
+# Verify that a failed direct binlog write no longer triggers a semisync
+# wait for a transaction that was never registered: the query should just
+# return a clean write error, and the server must remain fully responsive
+# (in particular, no assertion failure / crash).
+#
+--source include/have_debug.inc
+--source include/have_binlog_format_mixed_or_statement.inc
+
+call mtr.add_suppression("Write to binary log failed*");
+
+SET GLOBAL rpl_semi_sync_master_enabled = 1;
+SET GLOBAL rpl_semi_sync_master_wait_point = 'AFTER_SYNC';
+
+--let $query= CREATE TABLE t1 (i INT)
+--source include/binlog_inject_error.inc
+
+# The server must still be fully alive and responsive here -- this is the
+# actual regression check: pre-fix, the statement above aborts the
+# (debug-build) server via DBUG_ASSERT instead of returning cleanly.
+SELECT 1;
+SHOW STATUS LIKE 'Rpl_semi_sync_master_status';
+
+SET GLOBAL rpl_semi_sync_master_enabled = 0;
+SET GLOBAL rpl_semi_sync_master_wait_point = DEFAULT;
+DROP TABLE IF EXISTS t1;
diff --git a/sql/log.cc b/sql/log.cc
index d70fe6b9170f7..72a8a9f91938a 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -7259,7 +7259,8 @@ bool MYSQL_BIN_LOG::write(Log_event *event_info, my_bool *with_annotate)
       mysql_mutex_assert_owner(&LOCK_after_binlog_sync);
       mysql_mutex_assert_not_owner(&LOCK_commit_ordered);
 #ifdef HAVE_REPLICATION
-      if (repl_semisync_master.wait_after_sync(log_file_name, offset))
+      if (likely(!error) &&
+          repl_semisync_master.wait_after_sync(log_file_name, offset))
       {
         error=1;
         /* error is already printed inside hook */