diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 6bfd44c1..beefd79d 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -22,6 +22,7 @@ Changelog
 [S] = Security fix (issues that are related to security)
 *********************************************
 
+2016-09-06 [O] Replaced hard-coded number "10000" with constant "FIRST_USER_CAT" (thread ID 78848) {eenemeenemuu}
 2016-07-19 [A] Added new options to "sort order of albums" (thread ID 78795) {eenemeenemuu}
 2016-05-24 [B] Correct possible failure to get update when curl must be used {ron4mac}
 2016-05-24 [C] Set table width to 100% on update.php {eenemeenemuu}
diff --git a/bridge/udb_base.inc.php b/bridge/udb_base.inc.php
index fd684c6c..3ff1b977 100644
--- a/bridge/udb_base.inc.php
+++ b/bridge/udb_base.inc.php
@@ -530,7 +530,7 @@ function list_users_query (&$user_count)
 			// This is the way we collect the data without a direct join to the forum's user table
 			// This query determines which users we need to collect usernames of - ie just those which have albums with pics
 			// and are on the page we are looking at
-			$sql  = "SELECT category - 10000 AS user_id "
+			$sql  = "SELECT category - ".FIRST_USER_CAT." AS user_id "
 					. "FROM {$CONFIG['TABLE_ALBUMS']} AS a "
 						. "INNER JOIN {$CONFIG['TABLE_PICTURES']} AS p ON p.aid = a.aid "
 					. "WHERE ((ISNULL(approved) OR approved='YES') "
diff --git a/catmgr.php b/catmgr.php
index c9b1981c..6ee9fa0b 100644
--- a/catmgr.php
+++ b/catmgr.php
@@ -609,7 +609,7 @@ function verify_children($parent, $cid)
 
     $description = $superCage->post->getEscaped('description');
 
-    cpg_db_query("INSERT INTO {$CONFIG['TABLE_CATEGORIES']} (pos, parent, name, description) VALUES (10000, $parent, '$name', '$description')");
+    cpg_db_query("INSERT INTO {$CONFIG['TABLE_CATEGORIES']} (pos, parent, name, description) VALUES (".FIRST_USER_CAT.", $parent, '$name', '$description')");
 
     //insert in categorymap
     $cid = cpg_db_last_insert_id();
diff --git a/include/functions.inc.php b/include/functions.inc.php
index 949b637e..b238d545 100644
--- a/include/functions.inc.php
+++ b/include/functions.inc.php
@@ -3202,17 +3202,17 @@ function cpg_get_system_thumb_list($search_folder = 'images/')
  * @return array
  **/
 
-function& cpg_get_system_thumb($filename, $user = 10001)
+function& cpg_get_system_thumb($filename, $user = FIRST_USER_CAT)
 {
     global $CONFIG;
 
     // Correct user_id
-    if ($user < 10000) {
-        $user += 10000;
+    if ($user < FIRST_USER_CAT) {
+        $user += FIRST_USER_CAT;
     }
 
-    if ($user == 10000) {
-        $user = 10001;
+    if ($user == FIRST_USER_CAT) {
+        $user = FIRST_USER_CAT + 1;
     }
 
     // Get image data for thumb
diff --git a/index.php b/index.php
index 82237626..278e439d 100644
--- a/index.php
+++ b/index.php
@@ -939,7 +939,7 @@ function list_cat_albums($cat, $catdata)
         return '';
     }
 
-    $cat_owner_id = ($cat > 10000)?(10000 - $cat):(10001);
+    $cat_owner_id = ($cat > FIRST_USER_CAT)?(FIRST_USER_CAT - $cat):(FIRST_USER_CAT + 1);
     $cpg_nopic_data = cpg_get_system_thumb('nopic.jpg', $cat_owner_id);
     $cpg_privatepic_data = cpg_get_system_thumb('private.jpg', $cat_owner_id);
 
diff --git a/sidebar.php b/sidebar.php
index 14d73edd..4a62af36 100644
--- a/sidebar.php
+++ b/sidebar.php
@@ -315,7 +315,7 @@ function get_tree_album_data($category,$dtree_parent) {
                 $pic_filter = ' '.str_replace('p.',$CONFIG['TABLE_PICTURES'].'.',$FORBIDDEN_SET);
         }
         if ($category == USER_GAL_CAT) {
-                $sql = "SELECT DISTINCT user_id, user_name FROM {$CONFIG['TABLE_USERS']}, {$CONFIG['TABLE_ALBUMS']} WHERE  10000 + {$CONFIG['TABLE_USERS']}.user_id = {$CONFIG['TABLE_ALBUMS']}.category ORDER BY user_name ASC";
+                $sql = "SELECT DISTINCT user_id, user_name FROM {$CONFIG['TABLE_USERS']}, {$CONFIG['TABLE_ALBUMS']} WHERE  ".FIRST_USER_CAT." + {$CONFIG['TABLE_USERS']}.user_id = {$CONFIG['TABLE_ALBUMS']}.category ORDER BY user_name ASC";
                 $result = cpg_db_query($sql);
                 if (($cat_count = $result->numRows()) > 0) {
                         $rowset = cpg_db_fetch_rowset($result);
diff --git a/update.php b/update.php
index 137adec0..30364ce4 100644
--- a/update.php
+++ b/update.php
@@ -484,6 +484,7 @@ function update_tables()
     $sql_query = fread(fopen($db_update, 'r'), filesize($db_update));
     // Update table prefix
     $sql_query = preg_replace('/CPG_/', $CONFIG['TABLE_PREFIX'], $sql_query);
+    //$sql_query = str_replace('{FIRST_USER_CAT}', FIRST_USER_CAT, $sql_query);
 
     $sql_query = remove_remarks($sql_query);
     $sql_query = split_sql_file($sql_query, ';');