diff --git a/plugins/libcalendaring/tests/RecurrenceTest.php b/plugins/libcalendaring/tests/RecurrenceTest.php
index eeb922ad..7e9b0a85 100644
--- a/plugins/libcalendaring/tests/RecurrenceTest.php
+++ b/plugins/libcalendaring/tests/RecurrenceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Roundcube\Tests\StderrMock;
+
 /**
  * libcalendaring_recurrence tests
  *