MANIFEST                       |  1 +
 lib/PublicInbox/IMAPTracker.pm | 19 +++++++++++++++++--
 t/imap_tracker.t               | 26 ++++++++++++++++++++++++++

diff --git a/MANIFEST b/MANIFEST
index 42a00d7434425d7f346f5204f51dcc5ea72101c2..158d7ca2d8e50279e1133051565b127ee47e53e7 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -274,6 +274,7 @@ t/httpd.t
 t/hval.t
 t/imap.t
 t/imap_searchqp.t
+t/imap_tracker.t
 t/imapd-tls.t
 t/imapd.t
 t/import.t
diff --git a/lib/PublicInbox/IMAPTracker.pm b/lib/PublicInbox/IMAPTracker.pm
index c7da422b725f0c9d8cab1c8bb3ccdb22aa7898c6..bb4a39cc41a64968b526a09d3f4fe4b972ba8ec0 100644
--- a/lib/PublicInbox/IMAPTracker.pm
+++ b/lib/PublicInbox/IMAPTracker.pm
@@ -52,8 +52,23 @@ 	$sth->execute($url, $validity, $last);
 }
 
 sub new {
-	my ($class) = @_;
-	my $dbname = PublicInbox::Config->config_dir() . "/imap.sqlite3";
+	my ($class, $dbname) = @_;
+
+	# original name for compatibility with old setups:
+	$dbname //= PublicInbox::Config->config_dir() . "/imap.sqlite3";
+
+	# use the new XDG-compliant name for new setups:
+	if (!-f $dbname) {
+		$dbname = ($ENV{XDG_DATA_HOME} //
+			(($ENV{HOME} // '/nonexistent').'/.local/share')) .
+			'/public-inbox/imap.sqlite3';
+	}
+	if (!-f $dbname) {
+		require File::Path;
+		require File::Basename;;
+		File::Path::mkpath(File::Basename::dirname($dbname));
+	}
+
 	my $dbh = dbh_new($dbname);
 	bless { dbname => $dbname, dbh => $dbh }, $class;
 }
diff --git a/t/imap_tracker.t b/t/imap_tracker.t
new file mode 100644
index 0000000000000000000000000000000000000000..8dc04ed77a3accde000bd6700616c215da1d0f46
--- /dev/null
+++ b/t/imap_tracker.t
@@ -0,0 +1,26 @@
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use Test::More;
+use strict;
+use PublicInbox::TestCommon;
+require_mods 'DBD::SQLite';
+use_ok 'PublicInbox::IMAPTracker';
+my ($tmpdir, $for_destroy) = tmpdir();
+mkdir "$tmpdir/old" or die "mkdir $tmpdir/old: $!";
+my $old = "$tmpdir/old/imap.sqlite3";
+my $cur = "$tmpdir/data/public-inbox/imap.sqlite3";
+{
+	local $ENV{XDG_DATA_HOME} = "$tmpdir/data";
+	local $ENV{PI_DIR} = "$tmpdir/old";
+
+	my $tracker = PublicInbox::IMAPTracker->new;
+	ok(-f $cur, '->new creates file');
+	$tracker = undef;
+	ok(-f $cur, 'file persists after DESTROY');
+	link $cur, $old or die "link $cur => $old: $!";
+	unlink $cur or die "unlink $cur: $!";
+	$tracker = PublicInbox::IMAPTracker->new;
+	ok(!-f $cur, '->new does not create new file if old is present');
+}
+
+done_testing;