diff --git a/apache/apache-lib.pl b/apache/apache-lib.pl
index 3364b9045..83280a967 100755
--- a/apache/apache-lib.pl
+++ b/apache/apache-lib.pl
@@ -1991,29 +1991,56 @@ return @rv;
 # or undef.
 sub test_config
 {
-if ($httpd_modules{'core'} >= 1.301) {
-	# Test the configuration with the available command
-	local $cmd;
-	if ($config{'test_apachectl'} &&
-	    -x &translate_filename($config{'apachectl_path'})) {
-		# Test with apachectl
-		$cmd = "\"$config{'apachectl_path'}\" configtest";
-		}
-	else {
-		# Test with httpd
-		local $httpd = &find_httpd();
-		$cmd = "\"$httpd\" -d \"$config{'httpd_dir'}\" -t";
-		if ($config{'httpd_conf'}) {
-			$cmd .= " -f \"$config{'httpd_conf'}\"";
-			}
-		foreach $d (&get_httpd_defines()) {
-			$cmd .= " -D$d";
-			}
-		}
-	local $out = &backquote_command("$cmd 2>&1");
-	if ($out && $out !~ /(syntax|Checking).*\s+ok/i) {
-		return $out;
+return undef if ($httpd_modules{'core'} < 1.301);
+my $okre = qr/(syntax|Checking).*\s+ok/i;
+
+# Build the httpd command from the configured paths
+my $httpd = &find_httpd();
+my $httpdcmd = "\"$httpd\" -d \"$config{'httpd_dir'}\"";
+if ($config{'httpd_conf'}) {
+	$httpdcmd .= " -f \"$config{'httpd_conf'}\"";
+	}
+foreach my $d (&get_httpd_defines()) {
+	$httpdcmd .= " -D$d";
+	}
+
+# Pick the standard test command
+my ($cmd, $apachectl);
+if ($config{'test_apachectl'} &&
+    -x &translate_filename($config{'apachectl_path'})) {
+	# Test with apachectl, which may set up environment the config needs
+	$apachectl = "\"$config{'apachectl_path'}\"";
+	$cmd = "$apachectl configtest";
+	}
+else {
+	# Test with httpd
+	$cmd = "$httpdcmd -t";
+	}
+
+# Without a global ServerName, Apache looks up the system hostname in DNS
+# while loading the config, which stalls the test when DNS is slow. So first
+# try the test with a placeholder ServerName. Apache applies -C directives
+# before reading the config files, so a ServerName that this check misses,
+# such as one inside an IfModule section, still takes effect.
+my $conf = &get_config();
+if ($conf && !&find_directive("ServerName", $conf)) {
+	my $noname = "-C \"ServerName localhost\"";
+	my $out = &backquote_command(
+		($apachectl ? "$apachectl $noname -t" : "$httpdcmd $noname -t").
+		" 2>&1");
+	if ($apachectl && $httpd && $out =~ /no\s+longer\s+supported/i) {
+		# Red Hat's apachectl refuses extra arguments, and its
+		# configtest just runs httpd -t, so test with httpd instead
+		$out = &backquote_command("$httpdcmd $noname -t 2>&1");
 		}
+	return undef if ($out =~ $okre);
+	}
+
+# Run the standard test. This also runs when the quick test failed, in case
+# the extra arguments, rather than the config, caused the failure.
+my $out = &backquote_command("$cmd 2>&1");
+if ($out && $out !~ $okre) {
+	return $out;
 	}
 return undef;
 }
diff --git a/apache/t/test-config.t b/apache/t/test-config.t
new file mode 100644
index 000000000..203b7d8ea
--- /dev/null
+++ b/apache/t/test-config.t
@@ -0,0 +1,256 @@
+#!/usr/bin/perl
+# Tests for test_config, which must check the Apache config without waiting
+# on a DNS lookup of the system hostname.
+
+use strict;
+use warnings;
+use Test::More;
+use File::Basename qw(dirname);
+use File::Path qw(make_path);
+use File::Spec;
+use File::Temp qw(tempdir);
+use Cwd qw(abs_path);
+
+my $root = abs_path(File::Spec->catdir(dirname(__FILE__), '..', '..'));
+my $tmp = abs_path(tempdir(CLEANUP => 1));
+my $webmin_config = File::Spec->catdir($tmp, 'webmin-config');
+my $webmin_var = File::Spec->catdir($tmp, 'webmin-var');
+my $bin = File::Spec->catdir($tmp, 'bin');
+my $log = File::Spec->catfile($tmp, 'commands.log');
+
+# Paths with spaces check that the configured paths are used and quoted
+my $apache_root = File::Spec->catdir($tmp, 'apache root');
+my $apache_conf = File::Spec->catfile($apache_root, 'main config.conf');
+
+make_path($webmin_config, $webmin_var, "$webmin_config/apache",
+	  "$webmin_var/apache", $apache_root, $bin);
+
+# write_text(file, text, [mode])
+# Writes a file, optionally setting its permissions
+sub write_text
+{
+my ($file, $text, $mode) = @_;
+open(my $fh, '>', $file) || die "Failed to write $file: $!";
+print $fh $text;
+close($fh) || die "Failed to close $file: $!";
+chmod($mode, $file) || die "Failed to chmod $file: $!" if (defined($mode));
+}
+
+# Shell snippet that logs the program name and its arguments, one per field
+my $log_args = <<'EOF';
+{ printf '%s' "$FAKE_NAME"; for a in "$@"; do printf '|%s' "$a"; done;
+  printf '\n'; } >> "$FAKE_APACHE_LOG"
+EOF
+
+# Fake httpd, which passes or fails the test based on the environment
+my $httpd = File::Spec->catfile($bin, 'httpd');
+write_text($httpd, "#!/bin/sh\nFAKE_NAME=httpd\n".$log_args.<<'EOF', 0755);
+if [ "$FAKE_APACHE_RESULT" = "error" ]; then
+	echo "AH00526: Syntax error on line 2 of test.conf:"
+	echo "Invalid command 'Bogus', perhaps misspelled"
+	exit 1
+fi
+echo "Syntax OK"
+EOF
+
+# Debian-style apache2ctl, which passes extra arguments to httpd
+my $debian_ctl = File::Spec->catfile($bin, 'debian-ctl');
+write_text($debian_ctl,
+	   "#!/bin/sh\nFAKE_NAME=apachectl\n".$log_args.<<"EOF", 0755);
+case "\$*" in
+configtest) exec "$httpd" -t ;;
+*) exec "$httpd" "\$@" ;;
+esac
+EOF
+
+# Red Hat-style apachectl, which refuses extra arguments
+my $redhat_ctl = File::Spec->catfile($bin, 'redhat-ctl');
+write_text($redhat_ctl,
+	   "#!/bin/sh\nFAKE_NAME=apachectl\n".$log_args.<<"EOF", 0755);
+if [ "x\$2" != "x" ]; then
+	echo "Passing arguments to httpd using apachectl is no longer supported."
+	exit 1
+fi
+case "\$1" in
+configtest|-t) exec "$httpd" -t ;;
+esac
+exit 2
+EOF
+
+# Wrapper that only understands configtest
+my $strict_ctl = File::Spec->catfile($bin, 'strict-ctl');
+write_text($strict_ctl,
+	   "#!/bin/sh\nFAKE_NAME=apachectl\n".$log_args.<<"EOF", 0755);
+case "\$1" in
+configtest) exec "$httpd" -t ;;
+esac
+echo "usage: apachectl configtest"
+exit 2
+EOF
+
+write_text(File::Spec->catfile($webmin_config, 'config'),
+	"os_type=debian-linux\n".
+	"os_version=12\n".
+	"real_os_type=Debian Linux\n".
+	"real_os_version=12\n");
+write_text(File::Spec->catfile($webmin_config, 'miniserv.conf'),
+	"root=$root\n");
+write_text(File::Spec->catfile($webmin_config, 'apache', 'config'),
+	"httpd_dir=$apache_root\n".
+	"httpd_path=$httpd\n".
+	"httpd_conf=$apache_conf\n".
+	"apachectl_path=$debian_ctl\n".
+	"httpd_version=2.4.57\n".
+	"test_apachectl=0\n".
+	"test_config=1\n");
+
+$ENV{'WEBMIN_CONFIG'} = $webmin_config;
+$ENV{'WEBMIN_VAR'} = $webmin_var;
+$ENV{'FOREIGN_MODULE_NAME'} = 'apache';
+$ENV{'FOREIGN_ROOT_DIRECTORY'} = $root;
+$ENV{'REMOTE_USER'} = 'root';
+$ENV{'FAKE_APACHE_LOG'} = $log;
+$ENV{'FAKE_APACHE_RESULT'} = 'ok';
+
+unshift(@INC, $root);
+require File::Spec->catfile($root, 'apache', 'apache-lib.pl');
+
+{
+	no warnings 'once';
+	$main::httpd_modules{'core'} = 2.4;
+}
+
+# set_apache_conf(text)
+# Writes the main Apache config file and clears the cached copy
+sub set_apache_conf
+{
+my ($text) = @_;
+write_text($apache_conf, $text);
+main::flush_config_cache();
+}
+
+# A ServerName inside a virtual host is not global, so Apache still looks up
+# the system hostname
+my $no_global_name = "Listen 80\n".
+		     "<VirtualHost *:80>\n".
+		     "    ServerName vhost.example\n".
+		     "</VirtualHost>\n";
+set_apache_conf($no_global_name);
+
+# Expected log lines for the fake commands
+my $noname = 'ServerName localhost';
+my $direct_fast = join('|', 'httpd', '-d', $apache_root, '-f', $apache_conf,
+		       '-C', $noname, '-t');
+my $direct_std = join('|', 'httpd', '-d', $apache_root, '-f', $apache_conf,
+		      '-t');
+my $ctl_fast = join('|', 'apachectl', '-C', $noname, '-t');
+my $ctl_std = 'apachectl|configtest';
+my $httpd_fast = join('|', 'httpd', '-C', $noname, '-t');
+my $httpd_std = 'httpd|-t';
+
+# run_test(test-apachectl, [apachectl-path], result)
+# Runs test_config with the given settings, and returns its result and the
+# commands it ran
+sub run_test
+{
+my ($use_ctl, $ctl, $result) = @_;
+no warnings 'once';
+$main::config{'test_apachectl'} = $use_ctl;
+$main::config{'apachectl_path'} = $ctl if ($ctl);
+$ENV{'FAKE_APACHE_RESULT'} = $result;
+unlink($log);
+my $err = main::test_config();
+my @cmds;
+if (open(my $fh, '<', $log)) {
+	chomp(@cmds = <$fh>);
+	close($fh);
+	}
+return ($err, \@cmds);
+}
+
+subtest 'httpd test skips the hostname lookup' => sub {
+	my ($err, $cmds) = run_test(0, undef, 'ok');
+	is($err, undef, 'valid config passes');
+	is_deeply($cmds, [ $direct_fast ],
+		  'httpd runs once with configured paths and ServerName');
+};
+
+subtest 'httpd test reports config errors' => sub {
+	my ($err, $cmds) = run_test(0, undef, 'error');
+	like($err, qr/Syntax error on line 2/, 'error output is returned');
+	is_deeply($cmds, [ $direct_fast, $direct_std ],
+		  'failure is confirmed with the standard test');
+};
+
+subtest 'Debian apachectl passes ServerName to httpd' => sub {
+	my ($err, $cmds) = run_test(1, $debian_ctl, 'ok');
+	is($err, undef, 'valid config passes');
+	is_deeply($cmds, [ $ctl_fast, $httpd_fast ],
+		  'apachectl runs httpd with the placeholder ServerName');
+};
+
+subtest 'Debian apachectl reports config errors' => sub {
+	my ($err, $cmds) = run_test(1, $debian_ctl, 'error');
+	like($err, qr/Syntax error on line 2/, 'error output is returned');
+	is_deeply($cmds, [ $ctl_fast, $httpd_fast, $ctl_std, $httpd_std ],
+		  'failure is confirmed with apachectl configtest');
+};
+
+subtest 'Red Hat apachectl falls back to httpd' => sub {
+	my ($err, $cmds) = run_test(1, $redhat_ctl, 'ok');
+	is($err, undef, 'valid config passes');
+	is_deeply($cmds, [ $ctl_fast, $direct_fast ],
+		  'httpd is run directly when apachectl refuses arguments');
+};
+
+subtest 'Red Hat apachectl reports config errors' => sub {
+	my ($err, $cmds) = run_test(1, $redhat_ctl, 'error');
+	like($err, qr/Syntax error on line 2/, 'error output is returned');
+	unlike($err, qr/no longer supported/,
+	       'apachectl refusal is not reported as a config error');
+	is_deeply($cmds, [ $ctl_fast, $direct_fast, $ctl_std, $httpd_std ],
+		  'failure is confirmed with apachectl configtest');
+};
+
+subtest 'unknown apachectl falls back to configtest' => sub {
+	my ($err, $cmds) = run_test(1, $strict_ctl, 'ok');
+	is($err, undef, 'valid config passes');
+	is_deeply($cmds, [ $ctl_fast, $ctl_std, $httpd_std ],
+		  'standard test runs when apachectl rejects the arguments');
+};
+
+subtest 'global ServerName uses only the standard test' => sub {
+	set_apache_conf("ServerName www.example.com\n".$no_global_name);
+	my ($err, $cmds) = run_test(0, undef, 'ok');
+	is($err, undef, 'valid config passes');
+	is_deeply($cmds, [ $direct_std ], 'httpd runs without a placeholder');
+
+	($err, $cmds) = run_test(1, $redhat_ctl, 'error');
+	like($err, qr/Syntax error on line 2/, 'error output is returned');
+	is_deeply($cmds, [ $ctl_std, $httpd_std ],
+		  'apachectl configtest runs as before');
+	set_apache_conf($no_global_name);
+};
+
+subtest 'global ServerName in an included file is found' => sub {
+	# Webmin expands includes with glob(), which splits paths on spaces
+	my $inc = File::Spec->catfile($tmp, 'servername.conf');
+	write_text($inc, "ServerName www.example.com\n");
+	set_apache_conf("Include $inc\n".$no_global_name);
+	my ($err, $cmds) = run_test(1, $debian_ctl, 'ok');
+	is($err, undef, 'valid config passes');
+	is_deeply($cmds, [ $ctl_std, $httpd_std ],
+		  'apachectl configtest runs as before');
+	unlink($inc);
+	set_apache_conf($no_global_name);
+};
+
+subtest 'old Apache versions are not tested' => sub {
+	no warnings 'once';
+	local $main::httpd_modules{'core'} = 1.3;
+	my ($err, $cmds) = run_test(0, undef, 'error');
+	is($err, undef, 'no error is reported');
+	is_deeply($cmds, [ ], 'no test command runs');
+};
+
+done_testing();