diff --git a/CHANGELOG b/CHANGELOG
index 8d6398e7141..20508b38630 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,8 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix PHP warnings on dummy QUOTA responses in Courier-IMAP 4.17.1 (#6374)
+
 RELEASE 1.3.7
 -------------
 - Fix PHP Warning: Use of undefined constant IDNA_DEFAULT on systems without php-intl (#6244)
diff --git a/program/lib/Roundcube/rcube_imap_generic.php b/program/lib/Roundcube/rcube_imap_generic.php
index 61564bb1aeb..7fce2d02c85 100644
--- a/program/lib/Roundcube/rcube_imap_generic.php
+++ b/program/lib/Roundcube/rcube_imap_generic.php
@@ -3126,6 +3126,11 @@ public function getQuota($mailbox = null)
                     list(, , $quota_root) = $this->tokenizeResponse($line, 3);
 
                     $quotas = $this->tokenizeResponse($line, 1);
+
+                    if (empty($quotas)) {
+                        continue;
+                    }
+
                     foreach (array_chunk($quotas, 3) as $quota) {
                         list($type, $used, $total) = $quota;
                         $type = strtolower($type);