lib/PublicInbox/Daemon.pm   | 10 +++++++++-
 lib/PublicInbox/Listener.pm |  1 -
 t/common.perl               |  7 +++++--

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index 2b7ac266dfabbccfa83c106c0a114d2f1a446faf..2046a7f5abffd382d8a79f2e7aa2c5ee1d923432 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -155,9 +155,9 @@ 		my $prev = umask 0000;
 		my $s = eval { $sock_pkg->new(%o) };
 		warn "error binding $l: $! ($@)\n" unless $s;
 		umask $prev;
-
 		if ($s) {
 			$listener_names{sockname($s)} = $s;
+			$s->blocking(0);
 			push @listeners, $s;
 		}
 	}
@@ -363,6 +363,14 @@ 	my @rv = ();
 	foreach my $fd (3..$end) {
 		my $s = IO::Handle->new_from_fd($fd, 'r');
 		if (my $k = sockname($s)) {
+			if ($s->blocking) {
+				$s->blocking(0);
+				warn <<"";
+Inherited socket (fd=$fd) is blocking, making it non-blocking.
+Set 'NonBlocking = true' in the systemd.service unit to avoid stalled
+processes when multiple service instances start.
+
+			}
 			$listener_names{$k} = $s;
 			push @rv, $s;
 		} else {
diff --git a/lib/PublicInbox/Listener.pm b/lib/PublicInbox/Listener.pm
index 594dabb83e38eacd2b2733c952c205e3ffdc2456..604289343260a54f22790795c20ead9b7d8c85da 100644
--- a/lib/PublicInbox/Listener.pm
+++ b/lib/PublicInbox/Listener.pm
@@ -16,7 +16,6 @@ 	my ($class, $s, $cb) = @_;
 	setsockopt($s, SOL_SOCKET, SO_KEEPALIVE, 1);
 	setsockopt($s, IPPROTO_TCP, TCP_NODELAY, 1); # ignore errors on non-TCP
 	listen($s, 1024);
-	IO::Handle::blocking($s, 0);
 	my $self = fields::new($class);
 	$self->SUPER::new($s, EPOLLIN|EPOLLET|EPOLLEXCLUSIVE);
 	$self->{post_accept} = $cb;
diff --git a/t/common.perl b/t/common.perl
index 3f05b68a368403d7acecac6b9b83ab0b7a87aa12..91d65c5fa380a41b47420993198a57dfada4bc6d 100644
--- a/t/common.perl
+++ b/t/common.perl
@@ -24,15 +24,18 @@ 		ReuseAddr => 1,
 		Proto => 'tcp',
 		Type => Socket::SOCK_STREAM(),
 		Listen => 1024,
+		Blocking => 0,
 	)
 }
 
 sub unix_server ($) {
-	IO::Socket::UNIX->new(
+	my $s = IO::Socket::UNIX->new(
 		Listen => 1024,
 		Type => Socket::SOCK_STREAM(),
 		Local => $_[0],
-	)
+	);
+	$s->blocking(0);
+	$s;
 }
 
 sub spawn_listener {