diff --git a/changelog.txt b/changelog.txt
index c66978a..08b9f0c 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -2,6 +2,10 @@ FiveFilters.org: Full-Text RSS
 http://fivefilters.org/content-only/
 CHANGELOG
 ------------------------------------
+3.8.1 (2017-10-31)
+ - Bug fix: Systems with old ICU library produced an idn_to_ascii() error
+ - Compatibility test file updated to check for DOM extension
+
 3.8 (2017-09-25)
  - New site config directive: strip_attr: XPath attribute selector (e.g. //img/@srcset) - remove attribute from element
  - New site config directive: insert_detected_image: yes/no (default yes) - places image in og:image in the body if no other images extracted
diff --git a/ftr_compatibility_test.php b/ftr_compatibility_test.php
index 4ce9161..100b982 100644
--- a/ftr_compatibility_test.php
+++ b/ftr_compatibility_test.php
@@ -33,6 +33,7 @@ $allow_url_fopen_ok = (bool)ini_get('allow_url_fopen');
 $filter_ok = extension_loaded('filter');
 $gumbo_ok = class_exists('Layershifter\Gumbo\Parser');
 $idn_ok = function_exists('idn_to_ascii');
+$dom_ok = extension_loaded('DOM');
 
 if (extension_loaded('xmlreader')) {
 	$xml_ok = true;
@@ -257,7 +258,12 @@ div.chunk {
 						<td><a href="http://www.php.net/manual/en/filesystem.configuration.php#ini.allow-url-fopen">allow_url_fopen</a></td>
 						<td>Enabled</td>
 						<td><?php echo ($allow_url_fopen_ok) ? 'Enabled' : 'Disabled'; ?></td>
-					</tr>						
+					</tr>
+					<tr class="<?php echo ($dom_ok) ? 'enabled' : 'disabled'; ?>">
+						<td><a href="http://php.net/manual/en/book.dom.php">DOM / XML extension</a></td>
+						<td>Enabled</td>
+						<td><?php echo ($dom_ok) ? 'Enabled' : 'Disabled'; ?></td>
+					</tr>	
 				</tbody>
 			</table>
 		</div>
@@ -265,7 +271,7 @@ div.chunk {
 		<div class="chunk">
 			<h3>What does this mean?</h3>
 			<ol>
-				<?php if ($php_ok && $xml_ok && $pcre_ok && $mbstring_ok && $iconv_ok && $filter_ok && $zlib_ok && $tidy_ok && $curl_ok && $parallel_ok && $allow_url_fopen_ok): ?>
+				<?php if ($php_ok && $xml_ok && $pcre_ok && $dom_ok && $mbstring_ok && $iconv_ok && $filter_ok && $zlib_ok && $tidy_ok && $curl_ok && $parallel_ok && $allow_url_fopen_ok): ?>
 				<li>You have everything you need to run <?php echo $app_name; ?> properly!  Congratulations!</li>
 				<?php else: ?>
 					<?php if ($php_ok): ?>
diff --git a/libraries/humble-http-agent/HumbleHttpAgent.php b/libraries/humble-http-agent/HumbleHttpAgent.php
index db0040d..3b8adc9 100644
--- a/libraries/humble-http-agent/HumbleHttpAgent.php
+++ b/libraries/humble-http-agent/HumbleHttpAgent.php
@@ -270,7 +270,11 @@ class HumbleHttpAgent
 	public function convertIdn($url) {
 		if (function_exists('idn_to_ascii')) {
 			if ($host = @parse_url($url, PHP_URL_HOST)) {
-				$puny = idn_to_ascii($host, 0, INTL_IDNA_VARIANT_UTS46);
+				if (defined('INTL_IDNA_VARIANT_UTS46')) {
+					$puny = idn_to_ascii($host, 0, INTL_IDNA_VARIANT_UTS46);
+				} else {
+					$puny = idn_to_ascii($host);
+				}
 				if ($host != $puny) {
 					$pos = strpos($url, $host);
 					if ($pos !== false) {
diff --git a/makefulltextfeed.php b/makefulltextfeed.php
index 7592bf3..5289a83 100644
--- a/makefulltextfeed.php
+++ b/makefulltextfeed.php
@@ -1254,7 +1254,11 @@ function get_self_url() {
 function validate_url($url) {
 	if (function_exists('idn_to_ascii')) {
 		if ($host = @parse_url($url, PHP_URL_HOST)) {
-			$puny = idn_to_ascii($host, 0, INTL_IDNA_VARIANT_UTS46);
+			if (defined('INTL_IDNA_VARIANT_UTS46')) {
+				$puny = idn_to_ascii($host, 0, INTL_IDNA_VARIANT_UTS46);
+			} else {
+				$puny = idn_to_ascii($host);
+			}
 			if ($host != $puny) {
 				$pos = strpos($url, $host);
 				if ($pos !== false) {