diff --git a/cfg/posix.cfg b/cfg/posix.cfg
index 2eea93c60..436a60d94 100644
--- a/cfg/posix.cfg
+++ b/cfg/posix.cfg
@@ -1,4 +1,6 @@
 <?xml version="1.0"?>
+<!-- Description of the interfaces described by previous and current POSIX standards.
+     Current reference: http://pubs.opengroup.org/onlinepubs/9699919799/ -->
 <def format="2">
   <!-- http://man7.org/linux/man-pages/man3/a64l.3.html -->
   <!-- long a64l(const char *str64); -->
@@ -90,7 +92,7 @@
       <not-null/>
       <not-uninit/>
     </arg>
-    <arg nr="2">
+    <arg nr="3">
       <not-uninit/>
     </arg>
   </function>