diff --git a/plugins/libkolab/bin/modcache.sh b/plugins/libkolab/bin/modcache.sh
index 9285ec7a..da6e4f8f 100755
--- a/plugins/libkolab/bin/modcache.sh
+++ b/plugins/libkolab/bin/modcache.sh
@@ -157,7 +157,7 @@ default:
  */
 function resource_prefix($opts)
 {
-    return 'imap://' . urlencode($opts['username']) . '@' . $opts['host'] . '/';
+    return 'imap://' . str_replace('%', '\\%', urlencode($opts['username'])) . '@' . $opts['host'] . '/';
 }