diff --git a/admin/environment.xml b/admin/environment.xml
index a88b54b2639..b3d2fb2c387 100644
--- a/admin/environment.xml
+++ b/admin/environment.xml
@@ -257,6 +257,11 @@
           <ON_CHECK message="xmlrpcrecommended" />
         </FEEDBACK>
       </PHP_EXTENSION>
+      <PHP_EXTENSION name="soap" level="optional">
+        <FEEDBACK>
+          <ON_CHECK message="soaprecommended" />
+        </FEEDBACK>
+      </PHP_EXTENSION>
       <PHP_EXTENSION name="ctype" level="required">
         <FEEDBACK>
           <ON_ERROR message="ctyperequired" />
diff --git a/lang/en_utf8/admin.php b/lang/en_utf8/admin.php
index 606306744b8..3271b50a9a7 100644
--- a/lang/en_utf8/admin.php
+++ b/lang/en_utf8/admin.php
@@ -704,6 +704,7 @@ $string['smtphosts'] = 'SMTP hosts';
 $string['smtpmaxbulk'] = 'SMTP session limit';
 $string['smtppass'] = 'SMTP password';
 $string['smtpuser'] = 'SMTP username';
+$string['soaprecommended'] = 'Installing the optional soap extension is useful for web services and some contrib modules.';
 $string['spamcleaner'] = 'Spam cleaner';
 $string['stats'] = 'Statistics';
 $string['statscatdepth'] = 'Maximum parent categories';