diff --git a/README b/README
index 45b72e9acc..c5adda1776 100644
--- a/README
+++ b/README
@@ -137,7 +137,9 @@ run correctly.
 
 - PHP 5.2.3+. It may be possible to run this software on earlier
   versions of PHP, but many of the functions used are only available
-  in PHP 5.2 or above.
+  in PHP 5.2 or above. 5.2.6 or later is needed for XMPP background
+  daemons on 64-bit platforms. PHP 5.3.x should work but is known
+  to cause some failures for OpenID.
 - MySQL 5.x. The StatusNet database is stored, by default, in a MySQL
   server. It has been primarily tested on 5.x servers, although it may
   be possible to install on earlier (or later!) versions. The server