diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 570402a..ee7b124 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -2,7 +2,7 @@ use spamassassin_milter::ConfigBuilder;
 use std::{
     ffi::OsString,
     io::{ErrorKind, Read, Write},
-    net::{Ipv4Addr, Shutdown, SocketAddrV4, TcpListener},
+    net::{Ipv6Addr, Shutdown, SocketAddr, TcpListener},
     path::PathBuf,
     process::{Command, ExitStatus},
     thread::{self, JoinHandle},
@@ -14,7 +14,8 @@ use std::{
 // the configuration file location.
 pub fn isolate_from_spamc_conf(mut builder: ConfigBuilder) -> ConfigBuilder {
     // Must use `-F` instead of `--config` due to a bug in `spamc`.
-    builder.spamc_args(vec!["-F", "/dev/null"]);
+    // Additionally, `--log-to-stderr` avoids polluting syslog with test output.
+    builder.spamc_args(vec!["-F", "/dev/null", "--log-to-stderr"]);
     builder
 }
 
@@ -29,7 +30,7 @@ pub fn spawn_mock_spamd_server<F>(port: u16, f: F) -> JoinHandle<()>
 where
     F: Fn(String) -> HamOrSpam + Send + 'static,
 {
-    let socket_addr = SocketAddrV4::new(Ipv4Addr::LOCALHOST, port);
+    let socket_addr = SocketAddr::new(Ipv6Addr::LOCALHOST.into(), port);
     let timeout = Duration::from_secs(15);
 
     thread::spawn(move || {