diff --git a/language/operators.xml b/language/operators.xml
index db8693fe18..96c5d8a4a2 100644
--- a/language/operators.xml
+++ b/language/operators.xml
@@ -1220,10 +1220,11 @@ Expression: 0 = -4 << 62
    </para>
    <warning>
     <para>
-     Shifting integers by values greater than or equal to the system long
-     integer width results in undefined behavior. In other words, don't shift
-     more than 31 bits on a 32-bit system, and don't shift more than 63 bits on
-     a 64-bit system.
+     Prior to PHP 7.0, shifting integers by values greater than or equal to the
+     system long integer width, or by negative numbers, results in undefined
+     behavior. In other words, if you're using PHP 5.x, don't shift more than 31
+     bits on a 32-bit system, and don't shift more than 63 bits on 64-bit
+     system. 
     </para>
     <para>
      Use functions from the <link linkend="book.gmp">gmp</link> extension for