diff --git a/lib.php b/lib.php
index 27f7d7ace50b1c12a7be2a56b359db840c5dd1b1..abfe0630e2039b8085fb5d0259e40e4518b2a5d2 100644
--- a/lib.php
+++ b/lib.php
@@ -95,7 +95,11 @@ function local_sembasednav_extend_navigation(global_navigation $navigation)
     if ($specialNodesFirst == 1)
         add_semester_nodes($specialNodesList, $myCoursesNode);
 
-    $firstSemesterName = $mySemesters[array_key_first($mySemesters)]["name"];
+    if (count($mySemesters)) {
+        $firstSemesterName = $mySemesters[array_key_first($mySemesters)]["name"];
+    } else {
+        $firstSemesterName = null;
+    }
 
     if ($openFirstSemester && !is_null($firstSemesterName)) {
         $key = create_node_key($firstSemesterName);