diff --git a/mysql-test/suite/innodb_fts/r/misc_debug.result b/mysql-test/suite/innodb_fts/r/misc_debug.result
index 1fcc89b165b..8780e77bfdc 100644
--- a/mysql-test/suite/innodb_fts/r/misc_debug.result
+++ b/mysql-test/suite/innodb_fts/r/misc_debug.result
@@ -17,3 +17,14 @@ ALTER TABLE t ADD FULLTEXT INDEX (b(64));
 ERROR HY000: Unknown error
 SET SESSION debug_dbug=@saved_debug_dbug;
 DROP TABLE t;
+CREATE TABLE t1 (pk INT, a VARCHAR(8), PRIMARY KEY(pk)) ENGINE=InnoDB;
+CREATE TABLE t2 (b INT, FOREIGN KEY(b) REFERENCES t1(pk)) ENGINE=InnoDB;
+ALTER TABLE t1 ADD FULLTEXT KEY fk1(a);
+Warnings:
+Warning	124	InnoDB rebuilding table to add column FTS_DOC_ID
+DROP TABLE t1;
+ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails
+SET DEBUG_DBUG="+d,fts_instrument_sync";
+INSERT INTO t1 VALUES(1, "mariadb");
+ALTER TABLE t1 FORCE;
+DROP TABLE t2, t1;
diff --git a/mysql-test/suite/innodb_fts/t/misc_debug.test b/mysql-test/suite/innodb_fts/t/misc_debug.test
index 4b32afb848c..b33e4cfb25f 100644
--- a/mysql-test/suite/innodb_fts/t/misc_debug.test
+++ b/mysql-test/suite/innodb_fts/t/misc_debug.test
@@ -39,3 +39,16 @@ ALTER TABLE t ADD FULLTEXT INDEX (b(64));
 SET SESSION debug_dbug=@saved_debug_dbug;
 
 DROP TABLE t;
+
+# MDEV-21550 Assertion `!table->fts->in_queue' failed in
+# fts_optimize_remove_table
+CREATE TABLE t1 (pk INT, a VARCHAR(8), PRIMARY KEY(pk)) ENGINE=InnoDB;
+CREATE TABLE t2 (b INT, FOREIGN KEY(b) REFERENCES t1(pk)) ENGINE=InnoDB;
+ALTER TABLE t1 ADD FULLTEXT KEY fk1(a);
+--error ER_ROW_IS_REFERENCED_2
+DROP TABLE t1;
+SET DEBUG_DBUG="+d,fts_instrument_sync";
+INSERT INTO t1 VALUES(1, "mariadb");
+ALTER TABLE t1 FORCE;
+# Cleanup
+DROP TABLE t2, t1;
diff --git a/storage/innobase/fts/fts0opt.cc b/storage/innobase/fts/fts0opt.cc
index 202bd80d20a..deda14fee24 100644
--- a/storage/innobase/fts/fts0opt.cc
+++ b/storage/innobase/fts/fts0opt.cc
@@ -2645,8 +2645,6 @@ fts_optimize_request_sync_table(
 
 	ib_wqueue_add(fts_optimize_wq, msg, msg->heap, true);
 
-	table->fts->in_queue = true;
-
 	mutex_exit(&fts_optimize_wq->mutex);
 }
 
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index 708d2724595..0aa05a702f3 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -3806,6 +3806,11 @@ row_drop_table_for_mysql(
 			trx_commit_for_mysql(trx);
 		}
 
+		/* Add the table to fts queue if drop table fails */
+		if (err != DB_SUCCESS && table->fts) {
+			fts_optimize_add_table(table);
+		}
+
 		row_mysql_unlock_data_dictionary(trx);
 	}