diff --git a/application/models/tables/CourseCodes.php b/application/models/tables/CourseCodes.php
index f2a67f14da412be57cecb05d518d73d04487db5a..3321da8dffe69e291ed87415bafa56b75a88eccb 100644
--- a/application/models/tables/CourseCodes.php
+++ b/application/models/tables/CourseCodes.php
@@ -35,6 +35,10 @@ class CourseCodes extends Nmc_Db_Table
 
     public function findBySubjectNumberAndLetter($subject, $number, $letter = '')
     {
+        if (!$subject || !$number) {
+            return null;
+        }
+
         $where = array();
         $where[] = $this->_db->quoteInto('subject = ?', $subject);
         $where[] = $this->_db->quoteInto('courseNumber = ?', $number);