diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index eba7cad6ec36138f9982c6cc62212d6b4008d12d..f3344c6207d513f1d795fdc5cf3169df05d9d5f4 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -1617,4 +1617,6 @@ ResetSequenceCaches(void)
 		free(seqtab);
 		seqtab = next;
 	}
+
+	last_used_seq = NULL;
 }
diff --git a/src/test/regress/expected/sequence.out b/src/test/regress/expected/sequence.out
index 37e9a8cfa1afdea6b749b6813fbd6e5b4d0a08b0..8fcb70015fb58e5b22355e48f89fd2d25276d4aa 100644
--- a/src/test/regress/expected/sequence.out
+++ b/src/test/regress/expected/sequence.out
@@ -344,6 +344,9 @@ SELECT lastval();
       99
 (1 row)
 
+DISCARD SEQUENCES;
+SELECT lastval();
+ERROR:  lastval is not yet defined in this session
 CREATE SEQUENCE seq2;
 SELECT nextval('seq2');
  nextval 
diff --git a/src/test/regress/sql/sequence.sql b/src/test/regress/sql/sequence.sql
index 31cbc926c029a468c3407e2ad9d9f4e22bdb04b0..be5e9a97bf40e8c5afd8951faebd6fb0b491bdb8 100644
--- a/src/test/regress/sql/sequence.sql
+++ b/src/test/regress/sql/sequence.sql
@@ -154,6 +154,8 @@ SELECT nextval('seq');
 SELECT lastval();
 SELECT setval('seq', 99);
 SELECT lastval();
+DISCARD SEQUENCES;
+SELECT lastval();
 
 CREATE SEQUENCE seq2;
 SELECT nextval('seq2');