diff --git a/t/tags.t b/t/tags.t
index 8ff7ea0..1830d97 100644
--- a/t/tags.t
+++ b/t/tags.t
@@ -7,9 +7,13 @@ use utf8;
 use Test::More tests => 27;
 
 use Digest::MD5;
+use File::Basename;
 use IPC::Open3;
 use Symbol 'gensym';
 
+my $t = dirname(__FILE__);
+BAIL_OUT("'$t' contains unsupported characters") if $t !~ m|^[\w/]*$|;
+
 sub md5 {
 	my ($file) = @_;
 	open(my $fh, '<', $file) or return;
@@ -20,36 +24,36 @@ sub md5 {
 
 my $fh;
 
-is(md5('t/gobble.opus'), '111a483596ac32352fbce4d14d16abd2', 'the sample is the one we expect');
-is(`./opustags t/gobble.opus`, <<'EOF', 'read the initial tags');
+is(md5("$t/gobble.opus"), '111a483596ac32352fbce4d14d16abd2', 'the sample is the one we expect');
+is(`./opustags $t/gobble.opus`, <<'EOF', 'read the initial tags');
 encoder=Lavc58.18.100 libopus
 EOF
 
 # empty out.opus
-open($fh, '> t/out.opus') or die;
+open($fh, '>', "$t/out.opus") or die;
 close($fh);
-is(`./opustags t/gobble.opus -o t/out.opus 2>&1 >/dev/null`, <<'EOF', 'refuse to override');
-'t/out.opus' already exists (use -y to overwrite)
+is(`./opustags $t/gobble.opus -o $t/out.opus 2>&1 >/dev/null`, <<"EOF", 'refuse to override');
+'$t/out.opus' already exists (use -y to overwrite)
 EOF
-is(md5('t/out.opus'), 'd41d8cd98f00b204e9800998ecf8427e', 'the output wasn\'t written');
+is(md5("$t/out.opus"), 'd41d8cd98f00b204e9800998ecf8427e', 'the output wasn\'t written');
 is($?, 256, 'check the error code');
 
-is(`./opustags t/out.opus -o t/out.opus 2>&1 >/dev/null`, <<'EOF', 'output and input can\'t be the same');
+is(`./opustags $t/out.opus -o $t/out.opus 2>&1 >/dev/null`, <<'EOF', 'output and input can\'t be the same');
 error: the input and output files are the same
 EOF
 is($?, 256, 'check the error code');
 
-unlink('t/out.opus');
-is(`./opustags t/gobble.opus -o t/out.opus 2>&1`, '', 'copy the file without changes');
-is(md5('t/out.opus'), '111a483596ac32352fbce4d14d16abd2', 'the copy is faithful');
+unlink("$t/out.opus");
+is(`./opustags $t/gobble.opus -o $t/out.opus 2>&1`, '', 'copy the file without changes');
+is(md5("$t/out.opus"), '111a483596ac32352fbce4d14d16abd2', 'the copy is faithful');
 is($?, 0, 'check the error code');
 
-is(`./opustags --in-place t/out.opus -a A=B --add="A=C" --add "TITLE=Foo Bar" --delete A --add TITLE=七面鳥 --set encoder=whatever -s 1=2 -s X=1 -a X=2 -s X=3`, '', 'complex tag editing');
+is(`./opustags --in-place $t/out.opus -a A=B --add="A=C" --add "TITLE=Foo Bar" --delete A --add TITLE=七面鳥 --set encoder=whatever -s 1=2 -s X=1 -a X=2 -s X=3`, '', 'complex tag editing');
 is($?, 0, 'updating the tags went well');
-is(md5('t/out.opus'), '66780307a6081523dc9040f3c47b0448', 'check the footprint');
+is(md5("$t/out.opus"), '66780307a6081523dc9040f3c47b0448', 'check the footprint');
 
 $/ = undef;
-open($fh, './opustags t/out.opus |');
+open($fh, "./opustags $t/out.opus |");
 binmode($fh, ':utf8');
 is(<$fh>, <<'EOF', 'check the tags written');
 A=B
@@ -64,34 +68,34 @@ X=3
 EOF
 close($fh);
 
-is(`./opustags t/out.opus -d A -d foo -s X=4 -a TITLE=gobble -d TITLE`, <<'EOF', 'dry editing');
+is(`./opustags $t/out.opus -d A -d foo -s X=4 -a TITLE=gobble -d TITLE`, <<'EOF', 'dry editing');
 1=2
 encoder=whatever
 X=4
 TITLE=gobble
 EOF
-is(md5('t/out.opus'), '66780307a6081523dc9040f3c47b0448', 'the file did not change');
+is(md5("$t/out.opus"), '66780307a6081523dc9040f3c47b0448', 'the file did not change');
 
-is(`./opustags -i t/out.opus -a fatal=yes -a FOO -a BAR 2>&1`, <<'EOF', 'bad tag with --add');
+is(`./opustags -i $t/out.opus -a fatal=yes -a FOO -a BAR 2>&1`, <<'EOF', 'bad tag with --add');
 invalid comment: 'FOO'
 EOF
 is($?, 256, 'exited with a failure code');
-is(md5('t/out.opus'), '66780307a6081523dc9040f3c47b0448', 'the file did not change');
+is(md5("$t/out.opus"), '66780307a6081523dc9040f3c47b0448', 'the file did not change');
 
-is(`./opustags -i t/out.opus -s fatal=yes -s FOO -s BAR 2>&1`, <<'EOF', 'bad tag with --set');
+is(`./opustags -i $t/out.opus -s fatal=yes -s FOO -s BAR 2>&1`, <<'EOF', 'bad tag with --set');
 invalid comment: 'FOO'
 EOF
 is($?, 256, 'exited with a failure code');
-is(md5('t/out.opus'), '66780307a6081523dc9040f3c47b0448', 'the file did not change');
+is(md5("$t/out.opus"), '66780307a6081523dc9040f3c47b0448', 'the file did not change');
 
-is(`./opustags t/out.opus --delete-all -a OK=yes`, <<'EOF', 'delete all');
+is(`./opustags $t/out.opus --delete-all -a OK=yes`, <<'EOF', 'delete all');
 OK=yes
 EOF
 
 my ($pid, $pin, $pout, $perr);
 $perr = gensym;
 
-$pid = open3($pin, $pout, $perr, './opustags t/out.opus --set-all -a A=B -s X=Z -d OK');
+$pid = open3($pin, $pout, $perr, "./opustags $t/out.opus --set-all -a A=B -s X=Z -d OK");
 binmode($pin, ':utf8');
 binmode($pout, ':utf8');
 print $pin <<'EOF';
@@ -111,7 +115,7 @@ X=Z
 EOF
 waitpid($pid, 0);
 
-$pid = open3($pin, $pout, $perr, './opustags t/out.opus --set-all');
+$pid = open3($pin, $pout, $perr, "./opustags $t/out.opus --set-all");
 print $pin <<'EOF';
 whatever
 
@@ -131,4 +135,4 @@ EOF
 waitpid($pid, 0);
 is($?, 0, 'non fatal');
 
-unlink('t/out.opus');
+unlink("$t/out.opus");