diff --git a/mysql-test/r/innodb_mysql_sync.result b/mysql-test/r/innodb_mysql_sync.result
new file mode 100644
index 00000000000..039d8b74c07
--- /dev/null
+++ b/mysql-test/r/innodb_mysql_sync.result
@@ -0,0 +1,26 @@
+#
+# Bug 42074 concurrent optimize table and 
+# alter table = Assertion failed: thd->is_error()
+#
+DROP TABLE IF EXISTS t1;
+# Create InnoDB table
+CREATE TABLE t1 (id INT) engine=innodb;
+# Connection 1
+# Start optimizing table
+SET DEBUG_SYNC='ha_admin_try_alter SIGNAL optimize_started WAIT_FOR table_altered';
+OPTIMIZE TABLE t1;
+# Connection 2
+# Change table to engine=memory
+SET DEBUG_SYNC='now WAIT_FOR optimize_started';
+ALTER TABLE t1 engine=memory;
+SET DEBUG_SYNC='now SIGNAL table_altered';
+# Connection 1
+# Complete optimization
+Table	Op	Msg_type	Msg_text
+test.t1	optimize	note	Table does not support optimize, doing recreate + analyze instead
+test.t1	optimize	error	Got error -1 from storage engine
+test.t1	optimize	status	Operation failed
+Warnings:
+Error	1030	Got error -1 from storage engine
+DROP TABLE t1;
+SET DEBUG_SYNC='RESET';
diff --git a/mysql-test/t/innodb_mysql_sync.test b/mysql-test/t/innodb_mysql_sync.test
new file mode 100644
index 00000000000..3f061e30293
--- /dev/null
+++ b/mysql-test/t/innodb_mysql_sync.test
@@ -0,0 +1,48 @@
+#
+# Test file for InnoDB tests that require the debug sync facility
+#
+--source include/have_innodb.inc
+--source include/have_debug_sync.inc
+# Save the initial number of concurrent sessions.
+--source include/count_sessions.inc
+
+
+--echo #
+--echo # Bug 42074 concurrent optimize table and 
+--echo # alter table = Assertion failed: thd->is_error()
+--echo #
+
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+
+--echo # Create InnoDB table
+CREATE TABLE t1 (id INT) engine=innodb;
+connect (con2, localhost, root);
+
+--echo # Connection 1
+--echo # Start optimizing table
+connection default;
+SET DEBUG_SYNC='ha_admin_try_alter SIGNAL optimize_started WAIT_FOR table_altered';
+--send OPTIMIZE TABLE t1
+
+--echo # Connection 2
+--echo # Change table to engine=memory
+connection con2;
+SET DEBUG_SYNC='now WAIT_FOR optimize_started';
+ALTER TABLE t1 engine=memory;
+SET DEBUG_SYNC='now SIGNAL table_altered';
+
+--echo # Connection 1
+--echo # Complete optimization
+connection default;
+--reap
+
+disconnect con2;
+DROP TABLE t1;
+SET DEBUG_SYNC='RESET';
+
+
+# Check that all connections opened by test cases in this file are really
+# gone so execution of other tests won't be affected by their presence.
+--source include/wait_until_count_sessions.inc
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 532cb1465c6..6630331ad00 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -4878,6 +4878,7 @@ send_result_message:
       close_thread_tables(thd);
       if (!thd->locked_tables_mode)
         thd->mdl_context.release_all_locks();
+      DEBUG_SYNC(thd, "ha_admin_try_alter");
       protocol->store(STRING_WITH_LEN("note"), system_charset_info);
       protocol->store(STRING_WITH_LEN(
           "Table does not support optimize, doing recreate + analyze instead"),
@@ -4911,6 +4912,8 @@ send_result_message:
         if ((table->table= open_ltable(thd, table, lock_type, 0)) &&
             ((result_code= table->table->file->ha_analyze(thd, check_opt)) > 0))
           result_code= 0; // analyze went ok
+        if (result_code)  // analyze failed
+          table->table->file->print_error(result_code, MYF(0));
       }
       /* Start a new row for the final status row */
       protocol->prepare_for_resend();