diff --git a/mysql-test/suite/innodb/r/instant_alter_bugs.result b/mysql-test/suite/innodb/r/instant_alter_bugs.result
index 045b7468049..c630432585a 100644
--- a/mysql-test/suite/innodb/r/instant_alter_bugs.result
+++ b/mysql-test/suite/innodb/r/instant_alter_bugs.result
@@ -283,3 +283,15 @@ ALTER TABLE t CHANGE COLUMN alpha a INT WITHOUT SYSTEM VERSIONING,
 ALGORITHM=INSTANT;
 DROP TABLE t;
 set @@system_versioning_alter_history = error;
+#
+# MDEV-20117 Assertion 0 failed in row_sel_get_clust_rec_for_mysql
+#
+CREATE TABLE t (b INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t SET b=1;
+ALTER TABLE t ADD COLUMN a INT FIRST, ALGORITHM=INSTANT;
+DELETE FROM t;
+ALTER TABLE t ADD COLUMN c INT, ALGORITHM=INSTANT;
+ALTER TABLE t DROP COLUMN c, ALGORITHM=INSTANT;
+SELECT * FROM t;
+a	b
+DROP TABLE t;
diff --git a/mysql-test/suite/innodb/t/instant_alter_bugs.test b/mysql-test/suite/innodb/t/instant_alter_bugs.test
index fda8e88d70c..338d6972c43 100644
--- a/mysql-test/suite/innodb/t/instant_alter_bugs.test
+++ b/mysql-test/suite/innodb/t/instant_alter_bugs.test
@@ -293,3 +293,23 @@ ALTER TABLE t CHANGE COLUMN alpha a INT WITHOUT SYSTEM VERSIONING,
 ALGORITHM=INSTANT;
 DROP TABLE t;
 set @@system_versioning_alter_history = error;
+
+--echo #
+--echo # MDEV-20117 Assertion 0 failed in row_sel_get_clust_rec_for_mysql
+--echo #
+
+# This is not repeating the bug itself, but demonstrating that both
+# parts of the fix are needed.
+# To repeat the original bug, we should be somehow able to empty
+# the table of user records while purgeable undo log records exist.
+CREATE TABLE t (b INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t SET b=1;
+ALTER TABLE t ADD COLUMN a INT FIRST, ALGORITHM=INSTANT;
+DELETE FROM t;
+ALTER TABLE t ADD COLUMN c INT, ALGORITHM=INSTANT;
+# If page_cur_delete_rec() emptied the page (and wrongly reset the
+# page type) during the previous ALTER TABLE, the following would hit
+# an assertion failure because of root page type mismatch.
+ALTER TABLE t DROP COLUMN c, ALGORITHM=INSTANT;
+SELECT * FROM t;
+DROP TABLE t;
diff --git a/storage/innobase/handler/handler0alter.cc b/storage/innobase/handler/handler0alter.cc
index 14125272daf..ab3ec7ba249 100644
--- a/storage/innobase/handler/handler0alter.cc
+++ b/storage/innobase/handler/handler0alter.cc
@@ -5820,7 +5820,8 @@ add_all_virtual:
 	dberr_t err = DB_SUCCESS;
 	if (rec_is_metadata(rec, *index)) {
 		ut_ad(page_rec_is_user_rec(rec));
-		if (!page_has_next(block->frame)
+		if (!rec_is_alter_metadata(rec, *index)
+		    && !page_has_next(block->frame)
 		    && page_rec_is_last(rec, block->frame)) {
 			goto empty_table;
 		}
diff --git a/storage/innobase/page/page0cur.cc b/storage/innobase/page/page0cur.cc
index ded90c1c4f8..c2bdaee8c13 100644
--- a/storage/innobase/page/page0cur.cc
+++ b/storage/innobase/page/page0cur.cc
@@ -2327,7 +2327,8 @@ page_cur_delete_rec(
 	/* The record must not be the supremum or infimum record. */
 	ut_ad(page_rec_is_user_rec(current_rec));
 
-	if (page_get_n_recs(page) == 1 && !recv_recovery_is_on()) {
+	if (page_get_n_recs(page) == 1 && !recv_recovery_is_on()
+	    && !rec_is_alter_metadata(current_rec, *index)) {
 		/* Empty the page, unless we are applying the redo log
 		during crash recovery. During normal operation, the
 		page_create_empty() gets logged as one of MLOG_PAGE_CREATE,