diff --git a/src/test/modules/test_slot_timelines/expected/load_extension.out b/src/test/modules/test_slot_timelines/expected/load_extension.out
index 14a414aa7ed..7c2ad9d7c19 100644
--- a/src/test/modules/test_slot_timelines/expected/load_extension.out
+++ b/src/test/modules/test_slot_timelines/expected/load_extension.out
@@ -5,7 +5,7 @@ SELECT test_slot_timelines_create_logical_slot('test_slot', 'test_decoding');
  
 (1 row)
 
-SELECT test_slot_timelines_advance_logical_slot('test_slot', txid_current(), txid_current(), pg_current_xlog_location(), pg_current_xlog_location());
+SELECT test_slot_timelines_advance_logical_slot('test_slot', txid_current()::text::xid, txid_current()::text::xid, pg_current_xlog_location(), pg_current_xlog_location());
  test_slot_timelines_advance_logical_slot 
 ------------------------------------------
  
diff --git a/src/test/modules/test_slot_timelines/sql/load_extension.sql b/src/test/modules/test_slot_timelines/sql/load_extension.sql
index a71127d4716..24403552464 100644
--- a/src/test/modules/test_slot_timelines/sql/load_extension.sql
+++ b/src/test/modules/test_slot_timelines/sql/load_extension.sql
@@ -2,6 +2,6 @@ CREATE EXTENSION test_slot_timelines;
 
 SELECT test_slot_timelines_create_logical_slot('test_slot', 'test_decoding');
 
-SELECT test_slot_timelines_advance_logical_slot('test_slot', txid_current(), txid_current(), pg_current_xlog_location(), pg_current_xlog_location());
+SELECT test_slot_timelines_advance_logical_slot('test_slot', txid_current()::text::xid, txid_current()::text::xid, pg_current_xlog_location(), pg_current_xlog_location());
 
 SELECT pg_drop_replication_slot('test_slot');
diff --git a/src/test/modules/test_slot_timelines/test_slot_timelines--1.0.sql b/src/test/modules/test_slot_timelines/test_slot_timelines--1.0.sql
index 31d7f8ef1c1..a1886f732f1 100644
--- a/src/test/modules/test_slot_timelines/test_slot_timelines--1.0.sql
+++ b/src/test/modules/test_slot_timelines/test_slot_timelines--1.0.sql
@@ -3,14 +3,14 @@
 
 CREATE OR REPLACE FUNCTION test_slot_timelines_create_logical_slot(slot_name text, plugin text)
 RETURNS void
-LANGUAGE c AS 'MODULE_PATHNAME';
+STRICT LANGUAGE c AS 'MODULE_PATHNAME';
 
 COMMENT ON FUNCTION test_slot_timelines_create_logical_slot(text, text)
 IS 'Create a logical slot at a particular lsn and xid. Do not use in production servers, it is not safe. The slot is created with an invalid xmin and lsn.';
 
-CREATE OR REPLACE FUNCTION test_slot_timelines_advance_logical_slot(slot_name text, new_xmin bigint, new_catalog_xmin bigint, new_restart_lsn pg_lsn, new_confirmed_lsn pg_lsn)
+CREATE OR REPLACE FUNCTION test_slot_timelines_advance_logical_slot(slot_name text, new_xmin xid, new_catalog_xmin xid, new_restart_lsn pg_lsn, new_confirmed_lsn pg_lsn)
 RETURNS void
-LANGUAGE c AS 'MODULE_PATHNAME';
+STRICT LANGUAGE c AS 'MODULE_PATHNAME';
 
-COMMENT ON FUNCTION test_slot_timelines_advance_logical_slot(text, bigint, bigint, pg_lsn, pg_lsn)
+COMMENT ON FUNCTION test_slot_timelines_advance_logical_slot(text, xid, xid, pg_lsn, pg_lsn)
 IS 'Advance a logical slot directly. Do not use this in production servers, it is not safe.';
diff --git a/src/test/modules/test_slot_timelines/test_slot_timelines.c b/src/test/modules/test_slot_timelines/test_slot_timelines.c
index 74dd1a041b0..1f074881d2f 100644
--- a/src/test/modules/test_slot_timelines/test_slot_timelines.c
+++ b/src/test/modules/test_slot_timelines/test_slot_timelines.c
@@ -85,8 +85,8 @@ Datum
 test_slot_timelines_advance_logical_slot(PG_FUNCTION_ARGS)
 {
 	char	   *slotname = text_to_cstring(PG_GETARG_TEXT_P(0));
-	TransactionId new_xmin = (TransactionId) PG_GETARG_INT64(1);
-	TransactionId new_catalog_xmin = (TransactionId) PG_GETARG_INT64(2);
+	TransactionId new_xmin = DatumGetTransactionId(PG_GETARG_DATUM(1));
+	TransactionId new_catalog_xmin = DatumGetTransactionId(PG_GETARG_DATUM(2));
 	XLogRecPtr	restart_lsn = PG_GETARG_LSN(3);
 	XLogRecPtr	confirmed_lsn = PG_GETARG_LSN(4);
 
@@ -95,7 +95,7 @@ test_slot_timelines_advance_logical_slot(PG_FUNCTION_ARGS)
 	ReplicationSlotAcquire(slotname);
 
 	if (MyReplicationSlot->data.database != MyDatabaseId)
-		elog(ERROR, "Trying to update a slot on a different database");
+		elog(ERROR, "trying to update a slot on a different database");
 
 	MyReplicationSlot->data.xmin = new_xmin;
 	MyReplicationSlot->data.catalog_xmin = new_catalog_xmin;
diff --git a/src/test/recovery/t/006_logical_decoding_timelines.pl b/src/test/recovery/t/006_logical_decoding_timelines.pl
index bc20f405d78..a3a4b6150ae 100644
--- a/src/test/recovery/t/006_logical_decoding_timelines.pl
+++ b/src/test/recovery/t/006_logical_decoding_timelines.pl
@@ -172,8 +172,13 @@ is($stdout, '', 'No slots exist on the replica');
 # we're just doing it by hand for this test. This is exposing
 # postgres innards to SQL so it's unsafe except for testing.
 $node_master->safe_psql('postgres', 'CREATE EXTENSION test_slot_timelines;');
-my $slotinfo = $node_master->safe_psql('postgres',
-'SELECT slot_name, plugin, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn FROM pg_replication_slots ORDER BY slot_name'
+
+my $slotinfo = $node_master->safe_psql(
+	'postgres',
+	qq{SELECT slot_name, plugin,
+	COALESCE(xmin, '0'), catalog_xmin,
+	restart_lsn, confirmed_flush_lsn
+	FROM pg_replication_slots ORDER BY slot_name}
 );
 diag "Copying slots to replica";
 open my $fh, '<', \$slotinfo or die $!;
@@ -183,10 +188,7 @@ while (<$fh>)
 	chomp $_;
 	my ($slot_name, $plugin, $xmin, $catalog_xmin, $restart_lsn,
 		$confirmed_flush_lsn)
-	  = map {
-		if   ($_ ne '') { "'$_'" }
-		else            { 'NULL' }
-	  } split qr/\|/, $_;
+	  = map { "'$_'" } split qr/\|/, $_;
 
 	print
 "# Copying slot $slot_name,$plugin,$xmin,$catalog_xmin,$restart_lsn,$confirmed_flush_lsn\n";
@@ -208,7 +210,7 @@ is( $stdout,
 
 $stdout = $node_replica->safe_psql(
 	'postgres',
-	qq{SELECT slot_name, plugin, xmin, catalog_xmin,
+	qq{SELECT slot_name, plugin, COALESCE(xmin, '0'), catalog_xmin,
 			  restart_lsn, confirmed_flush_lsn
 		 FROM pg_replication_slots
 	 ORDER BY slot_name});
@@ -243,6 +245,7 @@ diag "oldest needed xlog seg is $oldest_needed_segment ";
 opendir(my $pg_xlog, $node_master->data_dir . "/pg_xlog") or die $!;
 while (my $seg = readdir $pg_xlog)
 {
+	next if $seg eq '.' or $seg eq '..';
 	next unless $seg >= $oldest_needed_segment && $seg =~ /^[0-9]{24}/;
 	diag "copying xlog seg $seg";
 	copy(