diff --git a/contrib/amcheck/t/001_verify_heapam.pl b/contrib/amcheck/t/001_verify_heapam.pl
index 39e16356d8..64ba64d6b4 100644
--- a/contrib/amcheck/t/001_verify_heapam.pl
+++ b/contrib/amcheck/t/001_verify_heapam.pl
@@ -7,7 +7,6 @@ use warnings;
 use PostgresNode;
 use TestLib;
 
-use Fcntl qw(:seek);
 use Test::More tests => 80;
 
 my ($node, $result);
@@ -127,8 +126,8 @@ sub corrupt_first_page
 	# Corrupt some line pointers.  The values are chosen to hit the
 	# various line-pointer-corruption checks in verify_heapam.c
 	# on both little-endian and big-endian architectures.
-	seek($fh, 32, SEEK_SET)
-	  or BAIL_OUT("seek failed: $!");
+	sysseek($fh, 32, 0)
+	  or BAIL_OUT("sysseek failed: $!");
 	syswrite(
 		$fh,
 		pack("L*",
diff --git a/src/bin/pg_amcheck/t/003_check.pl b/src/bin/pg_amcheck/t/003_check.pl
index cb4c86ad9e..4122d729d4 100644
--- a/src/bin/pg_amcheck/t/003_check.pl
+++ b/src/bin/pg_amcheck/t/003_check.pl
@@ -7,7 +7,6 @@ use warnings;
 use PostgresNode;
 use TestLib;
 
-use Fcntl qw(:seek);
 use Test::More tests => 63;
 
 my ($node, $port, %corrupt_page, %remove_relation);
@@ -90,8 +89,8 @@ sub corrupt_first_page
 	# Corrupt some line pointers.  The values are chosen to hit the
 	# various line-pointer-corruption checks in verify_heapam.c
 	# on both little-endian and big-endian architectures.
-	seek($fh, 32, SEEK_SET)
-	  or BAIL_OUT("seek failed: $!");
+	sysseek($fh, 32, 0)
+	  or BAIL_OUT("sysseek failed: $!");
 	syswrite(
 		$fh,
 		pack("L*",
diff --git a/src/bin/pg_amcheck/t/004_verify_heapam.pl b/src/bin/pg_amcheck/t/004_verify_heapam.pl
index 308fc61868..b603efad92 100644
--- a/src/bin/pg_amcheck/t/004_verify_heapam.pl
+++ b/src/bin/pg_amcheck/t/004_verify_heapam.pl
@@ -7,7 +7,6 @@ use warnings;
 use PostgresNode;
 use TestLib;
 
-use Fcntl qw(:seek);
 use Test::More;
 
 # This regression test demonstrates that the pg_amcheck binary correctly
@@ -99,8 +98,8 @@ sub read_tuple
 {
 	my ($fh, $offset) = @_;
 	my ($buffer, %tup);
-	seek($fh, $offset, SEEK_SET)
-	  or BAIL_OUT("seek failed: $!");
+	sysseek($fh, $offset, 0)
+	  or BAIL_OUT("sysseek failed: $!");
 	defined(sysread($fh, $buffer, HEAPTUPLE_PACK_LENGTH))
 	  or BAIL_OUT("sysread failed: $!");
 
@@ -165,8 +164,8 @@ sub write_tuple
 		$tup->{c_va_header},  $tup->{c_va_vartag},
 		$tup->{c_va_rawsize}, $tup->{c_va_extinfo},
 		$tup->{c_va_valueid}, $tup->{c_va_toastrelid});
-	seek($fh, $offset, SEEK_SET)
-	  or BAIL_OUT("seek failed: $!");
+	sysseek($fh, $offset, 0)
+	  or BAIL_OUT("sysseek failed: $!");
 	defined(syswrite($fh, $buffer, HEAPTUPLE_PACK_LENGTH))
 	  or BAIL_OUT("syswrite failed: $!");
 	return;
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 0db3e0a316..72a2cf8ac8 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -7,7 +7,6 @@ use Cwd;
 use Config;
 use File::Basename qw(basename dirname);
 use File::Path qw(rmtree);
-use Fcntl qw(:seek);
 use PostgresNode;
 use TestLib;
 use Test::More tests => 110;
@@ -40,7 +39,7 @@ if (open my $badchars, '>>', "$tempdir/pgdata/FOO\xe0\xe0\xe0BAR")
 }
 
 $node->set_replication_conf();
-system_or_bail 'pg_ctl', '-D', $pgdata, 'reload';
+$node->reload;
 
 $node->command_fails(
 	[ 'pg_basebackup', '-D', "$tempdir/backup" ],
@@ -555,17 +554,13 @@ my $file_corrupt2 = $node->safe_psql('postgres',
 	q{CREATE TABLE corrupt2 AS SELECT b FROM generate_series(1,2) AS b; ALTER TABLE corrupt2 SET (autovacuum_enabled=false); SELECT pg_relation_filepath('corrupt2')}
 );
 
-# set page header and block sizes
-my $pageheader_size = 24;
+# get block size for corruption steps
 my $block_size = $node->safe_psql('postgres', 'SHOW block_size;');
 
 # induce corruption
-system_or_bail 'pg_ctl', '-D', $pgdata, 'stop';
-open $file, '+<', "$pgdata/$file_corrupt1";
-seek($file, $pageheader_size, SEEK_SET);
-syswrite($file, "\0\0\0\0\0\0\0\0\0");
-close $file;
-system_or_bail 'pg_ctl', '-D', $pgdata, 'start';
+$node->stop;
+$node->corrupt_page_checksum($file_corrupt1, 0);
+$node->start;
 
 $node->command_checks_all(
 	[ 'pg_basebackup', '-D', "$tempdir/backup_corrupt" ],
@@ -576,16 +571,12 @@ $node->command_checks_all(
 rmtree("$tempdir/backup_corrupt");
 
 # induce further corruption in 5 more blocks
-system_or_bail 'pg_ctl', '-D', $pgdata, 'stop';
-open $file, '+<', "$pgdata/$file_corrupt1";
+$node->stop;
 for my $i (1 .. 5)
 {
-	my $offset = $pageheader_size + $i * $block_size;
-	seek($file, $offset, SEEK_SET);
-	syswrite($file, "\0\0\0\0\0\0\0\0\0");
+	$node->corrupt_page_checksum($file_corrupt1, $i * $block_size);
 }
-close $file;
-system_or_bail 'pg_ctl', '-D', $pgdata, 'start';
+$node->start;
 
 $node->command_checks_all(
 	[ 'pg_basebackup', '-D', "$tempdir/backup_corrupt2" ],
@@ -596,12 +587,9 @@ $node->command_checks_all(
 rmtree("$tempdir/backup_corrupt2");
 
 # induce corruption in a second file
-system_or_bail 'pg_ctl', '-D', $pgdata, 'stop';
-open $file, '+<', "$pgdata/$file_corrupt2";
-seek($file, $pageheader_size, SEEK_SET);
-syswrite($file, "\0\0\0\0\0\0\0\0\0");
-close $file;
-system_or_bail 'pg_ctl', '-D', $pgdata, 'start';
+$node->stop;
+$node->corrupt_page_checksum($file_corrupt2, 0);
+$node->start;
 
 $node->command_checks_all(
 	[ 'pg_basebackup', '-D', "$tempdir/backup_corrupt3" ],
diff --git a/src/bin/pg_checksums/t/002_actions.pl b/src/bin/pg_checksums/t/002_actions.pl
index 4cace1542d..761f7ab53b 100644
--- a/src/bin/pg_checksums/t/002_actions.pl
+++ b/src/bin/pg_checksums/t/002_actions.pl
@@ -9,7 +9,6 @@ use warnings;
 use PostgresNode;
 use TestLib;
 
-use Fcntl qw(:seek);
 use Test::More tests => 63;
 
 
@@ -24,6 +23,7 @@ sub check_relation_corruption
 	my $tablespace = shift;
 	my $pgdata     = $node->data_dir;
 
+	# Create table and discover its filesystem location.
 	$node->safe_psql(
 		'postgres',
 		"CREATE TABLE $table AS SELECT a FROM generate_series(1,10000) AS a;
@@ -37,9 +37,6 @@ sub check_relation_corruption
 	my $relfilenode_corrupted = $node->safe_psql('postgres',
 		"SELECT relfilenode FROM pg_class WHERE relname = '$table';");
 
-	# Set page header and block size
-	my $pageheader_size = 24;
-	my $block_size = $node->safe_psql('postgres', 'SHOW block_size;');
 	$node->stop;
 
 	# Checksums are correct for single relfilenode as the table is not
@@ -54,10 +51,7 @@ sub check_relation_corruption
 	);
 
 	# Time to create some corruption
-	open my $file, '+<', "$pgdata/$file_corrupted";
-	seek($file, $pageheader_size, SEEK_SET);
-	syswrite($file, "\0\0\0\0\0\0\0\0\0");
-	close $file;
+	$node->corrupt_page_checksum($file_corrupted, 0);
 
 	# Checksum checks on single relfilenode fail
 	$node->command_checks_all(
diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index c9016db6f8..92d9303e23 100644
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -2726,6 +2726,37 @@ sub pg_recvlogical_upto
 
 =pod
 
+=item $node->corrupt_page_checksum(self, file, page_offset)
+
+Intentionally corrupt the checksum field of one page in a file.
+The server must be stopped for this to work reliably.
+
+The file name should be specified relative to the cluster datadir.
+page_offset had better be a multiple of the cluster's block size.
+
+=cut
+
+sub corrupt_page_checksum
+{
+	my ($self, $file, $page_offset) = @_;
+	my $pgdata = $self->data_dir;
+	my $pageheader;
+
+	open my $fh, '+<', "$pgdata/$file" or die "open($file) failed: $!";
+	binmode $fh;
+	sysseek($fh, $page_offset, 0) or die "sysseek failed: $!";
+	sysread($fh, $pageheader, 24) or die "sysread failed: $!";
+	# This inverts the pd_checksum field (only); see struct PageHeaderData
+	$pageheader ^= "\0\0\0\0\0\0\0\0\xff\xff";
+	sysseek($fh, $page_offset, 0) or die "sysseek failed: $!";
+	syswrite($fh, $pageheader) or die "syswrite failed: $!";
+	close $fh;
+
+	return;
+}
+
+=pod
+
 =back
 
 =cut