diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index f0c842a607..14180ee469 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8781,3 +8781,16 @@ SELECT b, avg(a), max(a), count(*) FROM pagg_tab GROUP BY b HAVING sum(a) < 700
 
 -- Clean-up
 RESET enable_partitionwise_aggregate;
+-- Two-phase transactions are not supported.
+BEGIN;
+SELECT count(*) FROM ft1;
+ count 
+-------
+   822
+(1 row)
+
+-- error here
+PREPARE TRANSACTION 'fdw_tpc';
+ERROR:  cannot PREPARE a transaction that has operated on postgres_fdw foreign tables
+ROLLBACK;
+WARNING:  there is no transaction in progress
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 630b803e26..1c5c37b783 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2479,3 +2479,10 @@ SELECT b, avg(a), max(a), count(*) FROM pagg_tab GROUP BY b HAVING sum(a) < 700
 
 -- Clean-up
 RESET enable_partitionwise_aggregate;
+
+-- Two-phase transactions are not supported.
+BEGIN;
+SELECT count(*) FROM ft1;
+-- error here
+PREPARE TRANSACTION 'fdw_tpc';
+ROLLBACK;