--- wwsympa/SympaSession.pm.old	2016-12-04 10:49:21.983433301 +0100
+++ wwsympa/SympaSession.pm	2016-12-04 10:49:46.718916357 +0100
@@ -123,7 +123,7 @@
     }
 
     ## Load existing session.
-    if ($cookie and $cookie =~ /^\d{,16}$/) {
+    if ($cookie and $cookie =~ /^\d{1,16}$/) {
 	## Compatibility: session by older releases of Sympa.
 	$id_session = $cookie;
 	$is_old_session = 1;