diff --git a/language/operators.xml b/language/operators.xml
index 54d41b8177..b42ea5ea7c 100644
--- a/language/operators.xml
+++ b/language/operators.xml
@@ -232,9 +232,9 @@ $a = 1;
 $b = 2;
 $a = $b += 3; // $a = ($b += 3) -> $a = 5, $b = 5
 
-// mixing ++ and +
+// mixing ++ and + produces undefined behavior
 $a = 1;
-echo ++$a + $a++; // same as ++$a; echo $a + $a; $a++;
+echo ++$a + $a++; // may print 4 or 5
 ?>
 ]]>
      </programlisting>