diff --git a/lib/minimizer.php b/lib/minimizer.php
index 3310624596309cbba5c78878a62ffc02c8f4863b..db0c56f0f437a8771b981110fffd31991655aead 100644
--- a/lib/minimizer.php
+++ b/lib/minimizer.php
@@ -30,6 +30,12 @@ abstract class OC_Minimizer {
 			$cache->set($cache_key.'.gz', $gzout);
 			OC_Response::setETagHeader($etag);
 		}
+		// on some systems (e.g. SLES 11, but not Ubuntu) mod_deflate and zlib compression will compress the output twice. 
+		// This results in broken core.css and  core.js. To avoid it, we switch off zlib compression.
+		// Since mod_deflate is still active, Apache will compress what needs to be compressed, i.e. no disadvantage.
+		if(function_exists('apache_setenv') && ini_get('zlib.output_compression')) {
+                        ini_set('zlib.output_compression', 'Off');
+                }
 		if ($encoding = OC_Request::acceptGZip()) {
 			header('Content-Encoding: '.$encoding);
 			$out = $gzout;