diff --git a/src/docs/developer/unit_tests.diviner b/src/docs/developer/unit_tests.diviner
index bfcff05e73..a9a2ebfa72 100644
--- a/src/docs/developer/unit_tests.diviner
+++ b/src/docs/developer/unit_tests.diviner
@@ -49,7 +49,7 @@ Here's a simple example test:
     }
 
     public function testAllIsRightWithTheWorld() {
-      $this->assertEqual(4, 2 + 2, '2 + 2 = 4');
+      $this->assertEqual(4, $this->two + $this->two, '2 + 2 = 4');
     }
 
   }