diff --git a/CONFIGURE b/CONFIGURE
index 25af381332..4a7926f8c9 100644
--- a/CONFIGURE
+++ b/CONFIGURE
@@ -773,6 +773,13 @@ high: if you need high performance, or if you're seeing bad
       performance, set this to true. It will turn off some high-intensity code from
       the site.
 
+cache
+-----
+
+dir: A string path to a writable directory that will be used as temporary cache
+     for some functions (currently just the HtmlSanitizer).
+     If it is not set, the GNU social installation directory will be used.
+
 oldschool
 ---------
 
diff --git a/lib/util.php b/lib/util.php
index 62db64d828..9c32d74433 100644
--- a/lib/util.php
+++ b/lib/util.php
@@ -597,6 +597,9 @@ function common_purify($html)
     $cfg->set('Attr.AllowedRel', ['bookmark', 'directory', 'enclosure', 'home', 'license', 'nofollow', 'payment', 'tag']);  // http://microformats.org/wiki/rel
     $cfg->set('HTML.ForbiddenAttributes', array('style'));  // id, on* etc. are already filtered by default
     $cfg->set('URI.AllowedSchemes', array_fill_keys(common_url_schemes(), true));
+    if (common_config('cache', 'dir')) {
+        $cfg->set('Cache.SerializerPath', common_config('cache', 'dir'));
+    }
 
     // Remove more elements than what the default filter removes, default in GNU social are remotely
     // linked resources such as img, video, audio