diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c8dfa7c82..4c5fd3abea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -64,6 +64,7 @@
 - Fix whitespace handling in vCard line continuation (#9637)
 - Fix current script state after initial scripts creation in managesieve_kolab_master mode
 - Fix rcube_imap::get_vendor() result (and PHP warning) on Zimbra server (#9650)
+- Fix regression causing inline SVG images to be missing in mail preview (#9644)
 
 ## Release 1.6.9
 
diff --git a/program/lib/Roundcube/rcube_output.php b/program/lib/Roundcube/rcube_output.php
index 4e62f8ecc8..f0bc69b569 100644
--- a/program/lib/Roundcube/rcube_output.php
+++ b/program/lib/Roundcube/rcube_output.php
@@ -234,16 +234,16 @@ public function download_headers($filename, $params = [])
         if (!empty($params['type']) && is_string($params['type']) && strlen($params['type']) < 256
             && preg_match('/^[a-z0-9!#$&.+^_-]+\/[a-z0-9!#$&.+^_-]+$/i', $params['type'])
         ) {
-            $ctype = $params['type'];
+            $ctype = strtolower($params['type']);
         }
 
         // Send unsafe content as plain text
         if ($disposition == 'inline') {
-            if (preg_match('~(javascript|jscript|ecmascript|xml|html|text/)~i', $ctype)) {
+            if ($ctype != 'image/svg+xml' && preg_match('~(javascript|jscript|ecmascript|xml|html|text/)~', $ctype)) {
                 $ctype = 'text/plain';
             }
 
-            if (stripos($ctype, 'text') === 0) {
+            if (strpos($ctype, 'text') === 0) {
                 $charset = $this->charset;
                 if (!empty($params['type_charset']) && rcube_charset::is_valid($params['type_charset'])) {
                     $charset = $params['type_charset'];