t/mda_filter_rubylang.t   | 2 +-
 t/nntpd.t                 | 2 +-
 t/watch_filter_rubylang.t | 2 +-

diff --git a/t/mda_filter_rubylang.t b/t/mda_filter_rubylang.t
index dbcb275b397d470fa9cfdbc362d6d89fde658f8a..6f288b7ebbfb4075eb51cf77853a01791e18e104 100644
--- a/t/mda_filter_rubylang.t
+++ b/t/mda_filter_rubylang.t
@@ -18,7 +18,7 @@ is(system(@cfg, 'publicinboxmda.spamcheck', 'none'), 0);
 
 for my $v (qw(V1 V2)) {
 	my @warn;
-	$SIG{__WARN__} = sub { push @warn, @_ };
+	local $SIG{__WARN__} = sub { push @warn, @_ };
 	my $cfgpfx = "publicinbox.$v";
 	my $inboxdir = "$tmpdir/$v";
 	my $addr = "test-$v\@example.com";
diff --git a/t/nntpd.t b/t/nntpd.t
index 43b14d66389ab6544a38b22d453f33e7295f00f7..826e3f3da27c297a8c490593998045304f0009b6 100644
--- a/t/nntpd.t
+++ b/t/nntpd.t
@@ -268,7 +268,7 @@ 			my @mids = ("<$long_hdr>", '<2mid@wtf>');
 			$for_leafnode->header_set('Message-ID', @mids);
 			$for_leafnode->body_set('not-a-dupe');
 			my $warn = '';
-			$SIG{__WARN__} = sub { $warn .= join('', @_) };
+			local $SIG{__WARN__} = sub { $warn .= join('', @_) };
 			$im->add($for_leafnode);
 			$im->done;
 			like($warn, qr/reused/, 'warned for reused MID');
diff --git a/t/watch_filter_rubylang.t b/t/watch_filter_rubylang.t
index b4540660a79135659821c34276978d9427271b69..09217d94fcfa368e1215ec0a53ad252d5f0cc440 100644
--- a/t/watch_filter_rubylang.t
+++ b/t/watch_filter_rubylang.t
@@ -24,7 +24,7 @@ }
 
 for my $v (@v) {
 	my @warn;
-	$SIG{__WARN__} = sub { push @warn, @_ };
+	local $SIG{__WARN__} = sub { push @warn, @_ };
 	my $cfgpfx = "publicinbox.$v";
 	my $inboxdir = "$tmpdir/$v";
 	my $maildir = "$tmpdir/md-$v";