diff --git a/mysql-test/r/innodb_mysql_sync.result b/mysql-test/r/innodb_mysql_sync.result
index 58948835f66..8e210a7e205 100644
--- a/mysql-test/r/innodb_mysql_sync.result
+++ b/mysql-test/r/innodb_mysql_sync.result
@@ -153,5 +153,15 @@ SET DEBUG_SYNC= "now SIGNAL query";
 a	b
 # Test 4: Secondary unique index, should not block reads.
 # Connection default
+SET DEBUG_SYNC= "alter_table_manage_keys SIGNAL manage WAIT_FOR query";
+# Sending:
+ALTER TABLE t1 ADD UNIQUE (b);
+# Connection con1
+SET DEBUG_SYNC= "now WAIT_FOR manage";
+SELECT * FROM t1;
+a	b
+SET DEBUG_SYNC= "now SIGNAL query";
+# Connection default
+# Reaping: ALTER TABLE t1 ADD UNIQUE (b)
 SET DEBUG_SYNC= "RESET";
 DROP TABLE t1;
diff --git a/mysql-test/t/innodb_mysql_sync.test b/mysql-test/t/innodb_mysql_sync.test
index a8925306c70..bf1e5de1587 100644
--- a/mysql-test/t/innodb_mysql_sync.test
+++ b/mysql-test/t/innodb_mysql_sync.test
@@ -253,26 +253,23 @@ connection con1;
 --reap
 
 --echo # Test 4: Secondary unique index, should not block reads.
-# This requires HA_INPLACE_ADD_UNIQUE_INDEX_NO_WRITE to be supported
-# by InnoDB. Adding this flag currently introduces a regression so
-# this test is disabled until the regression has been fixed.
 
 --echo # Connection default
 connection default;
-#SET DEBUG_SYNC= "alter_table_manage_keys SIGNAL manage WAIT_FOR query";
-#--echo # Sending:
-#--send ALTER TABLE t1 ADD UNIQUE (b)
+SET DEBUG_SYNC= "alter_table_manage_keys SIGNAL manage WAIT_FOR query";
+--echo # Sending:
+--send ALTER TABLE t1 ADD UNIQUE (b)
 
-#--echo # Connection con1
-#connection con1;
-#SET DEBUG_SYNC= "now WAIT_FOR manage";
-#SELECT * FROM t1;
-#SET DEBUG_SYNC= "now SIGNAL query";
+--echo # Connection con1
+connection con1;
+SET DEBUG_SYNC= "now WAIT_FOR manage";
+SELECT * FROM t1;
+SET DEBUG_SYNC= "now SIGNAL query";
 
-#--echo # Connection default
-#connection default;
-#--echo # Reaping: ALTER TABLE t1 ADD UNIQUE (b)
-#--reap
+--echo # Connection default
+connection default;
+--echo # Reaping: ALTER TABLE t1 ADD UNIQUE (b)
+--reap
 
 disconnect con1;
 disconnect con2;
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 3763e6f9cef..bea92903c58 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -2597,6 +2597,7 @@ innobase_alter_table_flags(
 		| HA_INPLACE_ADD_INDEX_NO_WRITE
 		| HA_INPLACE_DROP_INDEX_NO_READ_WRITE
 		| HA_INPLACE_ADD_UNIQUE_INDEX_NO_READ_WRITE
+		| HA_INPLACE_ADD_UNIQUE_INDEX_NO_WRITE
 		| HA_INPLACE_DROP_UNIQUE_INDEX_NO_READ_WRITE
 		| HA_INPLACE_ADD_PK_INDEX_NO_READ_WRITE);
 }