lib/PublicInbox/LeiOverview.pm |  3 ++-
 lib/PublicInbox/LeiToMail.pm   |  6 +++++-
 lib/PublicInbox/LeiXSearch.pm  |  9 ++++++++-
 t/lei.t                        | 14 ++++++++++++++

diff --git a/lib/PublicInbox/LeiOverview.pm b/lib/PublicInbox/LeiOverview.pm
index 8781259addfb8bb33440dc7c337f4f1f15a59a7a..a7021b03d9246da2c4b584a0353ec73f58f17b40 100644
--- a/lib/PublicInbox/LeiOverview.pm
+++ b/lib/PublicInbox/LeiOverview.pm
@@ -82,7 +82,8 @@ 	}
 	if (!$json) {
 		# default to the cheapest sort since MUA usually resorts
 		$lei->{opt}->{'sort'} //= 'docid' if $dst ne '/dev/stdout';
-		$lei->{l2m} = PublicInbox::LeiToMail->new($lei);
+		$lei->{l2m} = eval { PublicInbox::LeiToMail->new($lei) };
+		return $lei->fail($@) if $@;
 	}
 	$lei->{dedupe} //= PublicInbox::LeiDedupe->new($lei);
 	$self;
diff --git a/lib/PublicInbox/LeiToMail.pm b/lib/PublicInbox/LeiToMail.pm
index a6e517ea50ee3da25b6aa30c7c20a15a37bf6a02..49b5c8ab4cbdb3cb04480725dee6e7473c38cbfd 100644
--- a/lib/PublicInbox/LeiToMail.pm
+++ b/lib/PublicInbox/LeiToMail.pm
@@ -339,8 +339,12 @@ 	my $dst = $lei->{ovv}->{dst};
 	my $self = bless {}, $cls;
 	if ($fmt eq 'maildir') {
 		$self->{base_type} = 'maildir';
+		-e $dst && !-d _ and die
+				"$dst exists and is not a directory\n";
 		$lei->{ovv}->{dst} = $dst .= '/' if substr($dst, -1) ne '/';
 	} elsif (substr($fmt, 0, 4) eq 'mbox') {
+		-e $dst && !-f _ && !-p _ and die
+				"$dst exists and is not a regular file\n";
 		$self->can("eml2$fmt") or die "bad mbox --format=$fmt\n";
 		$self->{base_type} = 'mbox';
 	} else {
@@ -374,7 +378,7 @@ 	for my $x (qw(tmp new cur)) {
 		my $d = $dst.$x;
 		next if -d $d;
 		require File::Path;
-		File::Path::mkpath($d) or die "mkpath($d): $!";
+		File::Path::mkpath($d);
 		-d $d or die "$d is not a directory";
 	}
 }
diff --git a/lib/PublicInbox/LeiXSearch.pm b/lib/PublicInbox/LeiXSearch.pm
index 002791c21b73075448c3fed56a428d1126ebd0f4..fa37543f32625d21fa25f4410a026f7467e30363 100644
--- a/lib/PublicInbox/LeiXSearch.pm
+++ b/lib/PublicInbox/LeiXSearch.pm
@@ -201,7 +201,14 @@
 sub do_post_augment {
 	my ($lei, $zpipe, $au_done) = @_;
 	my $l2m = $lei->{l2m} or die 'BUG: no {l2m}';
-	$l2m->post_augment($lei, $zpipe);
+	eval { $l2m->post_augment($lei, $zpipe) };
+	if (my $err = $@) {
+		if (my $lxs = delete $lei->{lxs}) {
+			$lxs->wq_kill;
+			$lxs->wq_close;
+		}
+		$lei->fail("$err");
+	}
 	close $au_done; # triggers wait_startq
 }
 
diff --git a/t/lei.t b/t/lei.t
index c804ff5916c5378e0795b3f8db4bf9571899e178..8bb4e439bfadbbc98171155e10a5317ab2528c20 100644
--- a/t/lei.t
+++ b/t/lei.t
@@ -181,6 +181,20 @@ 	});
 	$lei->('ls-external');
 	like($out, qr/boost=0\n/s, 'ls-external has output');
 
+	ok(!$lei->(qw(q s:prefix -o /dev/null -f maildir)), 'bad maildir');
+	like($err, qr!/dev/null exists and is not a directory!,
+		'error shown');
+	is($? >> 8, 1, 'errored out with exit 1');
+
+	ok(!$lei->(qw(q s:prefix -f mboxcl2 -o), $home), 'bad mbox');
+	like($err, qr!\Q$home\E exists and is not a regular file!,
+		'error shown');
+	is($? >> 8, 1, 'errored out with exit 1');
+
+	ok(!$lei->(qw(q s:prefix -o /dev/stdout -f Mbox2)), 'bad format');
+	like($err, qr/bad mbox --format=mbox2/, 'error shown');
+	is($? >> 8, 1, 'errored out with exit 1');
+
 	# note, on a Bourne shell users should be able to use either:
 	#	s:"use boolean prefix"
 	#	"s:use boolean prefix"