diff --git a/mod/data/tests/generator_test.php b/mod/data/tests/generator_test.php
index 24236894044..adf15730536 100644
--- a/mod/data/tests/generator_test.php
+++ b/mod/data/tests/generator_test.php
@@ -118,7 +118,9 @@ class mod_data_generator_testcase extends advanced_testcase {
 
         for ($i = 1; $i < $count; $i++) {
             $fieldname = 'field-' . $i;
-            $this->assertTrue(strpos($addtemplate, '[[' . $fieldname . ']]') >= 0);
+            $position = strpos($addtemplate, '[[' . $fieldname . ']]');
+            $this->assertIsNumeric($position);
+            $this->assertGreaterThanOrEqual(0, $position);
         }
     }