diff --git a/UPGRADING b/UPGRADING
index d4dd3033567..514662a5646 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -217,6 +217,7 @@ PHP 5.6 UPGRADE NOTES
 
 - Strings:
   substr_compare() now allows $length to be zero.
+  pack() and unpack() now support 64-bit format specifiers: q, Q, J and P.
 
 - Crypt:
   crypt() will now raise an E_NOTICE error if the salt parameter is omitted.