diff --git a/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c b/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c
index d83c17e..1fb0825 100644
--- a/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c
+++ b/infrastructure-centred/owlps-aggregator/owlps-aggregatord.c
@@ -13,7 +13,7 @@ char *program_name = NULL ;
 cfg_t *cfg = NULL ; // Configuration structure
 couple_list *couples = NULL ; // Computed data list
 ap_list *token_aps = NULL ; // Token ring of the APs
-unsigned int nb_aps = 0 ;
+unsigned int nb_aps = 0 ; // Number of APs in the AP ring
 
 
 
@@ -790,7 +790,6 @@ ap_list* add_ap_front(unsigned char mac_addr_bytes[6])
   memcpy(ap->mac_addr_bytes, mac_addr_bytes, 6) ;
   update_ap_seen(ap) ;
   push_ap(ap) ;
-  ++nb_aps ;
   return ap ;
 }
 
@@ -822,6 +821,8 @@ void push_ap(ap_list *ap)
 {
   assert(ap) ;
 
+  ++nb_aps ;
+
   if (token_aps == NULL) // List does not exist yet
     {
       token_aps = ap ;
@@ -872,12 +873,9 @@ void delete_old_aps()
 {
   struct timeval now ;
 
-  if (token_aps == NULL)
-    return ;
-
   gettimeofday(&now, NULL) ;
 
-  while (token_aps != token_aps->next)
+  while (token_aps != NULL)
     if (sub_date(token_aps->last_seen, now) >
         (unsigned long) cfg_getint(cfg, "ap_keep_timeout") * 1000)
       delete_ap(token_aps) ;
@@ -900,7 +898,6 @@ void delete_ap(ap_list *ap)
 
   unlink_ap(ap) ;
   free(ap) ;
-  --nb_aps ;
 }
 
 
@@ -924,12 +921,19 @@ void unlink_ap(ap_list *ap)
   ap_next->previous = ap_previous ;
 
   if (ap == token_aps)
-    token_aps = ap_next ;
+    {
+      if (ap->next == ap) // It was the last AP in the ring
+        token_aps = NULL ;
+      else
+        token_aps = ap_next ;
+    }
+
+  --nb_aps ;
 }
 
 
 /*
- * Sends a send order to the given AP.
+ * Sends a 'send' order to the given AP.
  */
 void order_send(ap_list *ap)
 {