diff --git a/admin/themes/default/template/cat_modify.tpl b/admin/themes/default/template/cat_modify.tpl
index 146f6734f..d625bf13e 100644
--- a/admin/themes/default/template/cat_modify.tpl
+++ b/admin/themes/default/template/cat_modify.tpl
@@ -106,7 +106,7 @@ jQuery(document).ready(function() {
 
   $(".deleteAlbum").on("click", function() {
     $.ajax({
-      url: "ws.php?format=json&method=pwg.images.calculateOrphansOnAlbumDeletion",
+      url: "ws.php?format=json&method=pwg.categories.calculateOrphans",
       type: "GET",
       data: {
         category_id: {$CAT_ID},
diff --git a/include/ws_functions/pwg.categories.php b/include/ws_functions/pwg.categories.php
index b7643bdfe..20ca842c5 100644
--- a/include/ws_functions/pwg.categories.php
+++ b/include/ws_functions/pwg.categories.php
@@ -1054,4 +1054,115 @@ SELECT id, name, dir
   }
 }
 
+/**
+ * API method
+ * Return the number of orphan photos if an album is deleted
+ */
+
+function ws_categories_calculateOrphans($param, &$service)
+{
+  global $conf;
+
+  $category_id = $param['category_id'][0];
+
+  $query = '
+SELECT DISTINCT 
+    category_id
+  FROM 
+    '.IMAGE_CATEGORY_TABLE.'
+  WHERE 
+    category_id = '.$category_id.'
+  LIMIT 1';
+  $result = pwg_query($query);
+  $category['has_images'] = pwg_db_num_rows($result)>0 ? true : false;
+
+  // number of sub-categories
+  $subcat_ids = get_subcat_ids(array($category_id));
+
+  $category['nb_subcats'] = count($subcat_ids) - 1;
+
+  // total number of images under this category (including sub-categories)
+  $query = '
+SELECT DISTINCT
+    (image_id)
+  FROM 
+    '.IMAGE_CATEGORY_TABLE.'
+  WHERE 
+    category_id IN ('.implode(',', $subcat_ids).')
+  ;';
+  $image_ids_recursive = query2array($query, null, 'image_id');
+
+  $category['nb_images_recursive'] = count($image_ids_recursive);
+
+  // number of images that would become orphan on album deletion
+  $category['nb_images_becoming_orphan'] = 0;
+  $category['nb_images_associated_outside'] = 0;
+
+  if ($category['nb_images_recursive'] > 0)
+  {
+    // if we don't have "too many" photos, it's faster to compute the orphans with MySQL
+    if ($category['nb_images_recursive'] < 1000)
+    {
+      $query = '
+  SELECT DISTINCT
+      (image_id)
+    FROM 
+      '.IMAGE_CATEGORY_TABLE.'
+    WHERE 
+      category_id 
+    NOT IN 
+      ('.implode(',', $subcat_ids).')
+    AND 
+      image_id 
+    IN 
+      ('.implode(',', $image_ids_recursive).')
+  ;';
+
+    $image_ids_associated_outside = query2array($query, null, 'image_id');
+    $category['nb_images_associated_outside'] = count($image_ids_associated_outside);
+
+    $image_ids_becoming_orphan = array_diff($image_ids_recursive, $image_ids_associated_outside);
+    $category['nb_images_becoming_orphan'] = count($image_ids_becoming_orphan);
+  }
+  // else it's better to avoid sending a huge SQL request, we compute the orphan list with PHP
+    else
+    {
+    $image_ids_recursive_keys = array_flip($image_ids_recursive);
+
+    $query = '
+  SELECT
+      image_id
+    FROM 
+      '.IMAGE_CATEGORY_TABLE.'
+    WHERE 
+      category_id 
+    NOT IN 
+      ('.implode(',', $subcat_ids).')
+  ;';
+    $image_ids_associated_outside = query2array($query, null, 'image_id');
+    $image_ids_not_orphan = array();
+
+    foreach ($image_ids_associated_outside as $image_id)
+    {
+      if (isset($image_ids_recursive_keys[$image_id]))
+      {
+        $image_ids_not_orphan[] = $image_id;
+      }
+    }
+
+    $category['nb_images_associated_outside'] = count(array_unique($image_ids_not_orphan));
+    $image_ids_becoming_orphan = array_diff($image_ids_recursive, $image_ids_not_orphan);
+    $category['nb_images_becoming_orphan'] = count($image_ids_becoming_orphan);
+  }
+}
+
+  $output[] = array(
+    'nb_images_associated_outside' => $category['nb_images_associated_outside'],
+    'nb_images_becoming_orphan' => $category['nb_images_becoming_orphan'],
+    'nb_images_recursive' => $category['nb_images_recursive'],
+  );
+  
+  return $output;
+}
+
 ?>
\ No newline at end of file
diff --git a/include/ws_functions/pwg.php b/include/ws_functions/pwg.php
index 2e953f27b..d05b30b9e 100644
--- a/include/ws_functions/pwg.php
+++ b/include/ws_functions/pwg.php
@@ -555,116 +555,4 @@ SELECT
   fclose($f);
 }
 
-
-/**
- * API method
- * Return the number of orphan photos if an album is deleted
- */
-
-function ws_images_calculateOrphansOnAlbumDeletion($param, &$service)
-{
-  global $conf;
-
-  $category_id = $param['category_id'][0];
-
-  $query = '
-SELECT DISTINCT 
-    category_id
-  FROM 
-    '.IMAGE_CATEGORY_TABLE.'
-  WHERE 
-    category_id = '.$category_id.'
-  LIMIT 1';
-  $result = pwg_query($query);
-  $category['has_images'] = pwg_db_num_rows($result)>0 ? true : false;
-
-  // number of sub-categories
-  $subcat_ids = get_subcat_ids(array($category_id));
-
-  $category['nb_subcats'] = count($subcat_ids) - 1;
-
-  // total number of images under this category (including sub-categories)
-  $query = '
-SELECT DISTINCT
-    (image_id)
-  FROM 
-    '.IMAGE_CATEGORY_TABLE.'
-  WHERE 
-    category_id IN ('.implode(',', $subcat_ids).')
-  ;';
-  $image_ids_recursive = query2array($query, null, 'image_id');
-
-  $category['nb_images_recursive'] = count($image_ids_recursive);
-
-  // number of images that would become orphan on album deletion
-  $category['nb_images_becoming_orphan'] = 0;
-  $category['nb_images_associated_outside'] = 0;
-
-  if ($category['nb_images_recursive'] > 0)
-  {
-    // if we don't have "too many" photos, it's faster to compute the orphans with MySQL
-    if ($category['nb_images_recursive'] < 1000)
-    {
-      $query = '
-  SELECT DISTINCT
-      (image_id)
-    FROM 
-      '.IMAGE_CATEGORY_TABLE.'
-    WHERE 
-      category_id 
-    NOT IN 
-      ('.implode(',', $subcat_ids).')
-    AND 
-      image_id 
-    IN 
-      ('.implode(',', $image_ids_recursive).')
-  ;';
-
-    $image_ids_associated_outside = query2array($query, null, 'image_id');
-    $category['nb_images_associated_outside'] = count($image_ids_associated_outside);
-
-    $image_ids_becoming_orphan = array_diff($image_ids_recursive, $image_ids_associated_outside);
-    $category['nb_images_becoming_orphan'] = count($image_ids_becoming_orphan);
-  }
-  // else it's better to avoid sending a huge SQL request, we compute the orphan list with PHP
-    else
-    {
-    $image_ids_recursive_keys = array_flip($image_ids_recursive);
-
-    $query = '
-  SELECT
-      image_id
-    FROM 
-      '.IMAGE_CATEGORY_TABLE.'
-    WHERE 
-      category_id 
-    NOT IN 
-      ('.implode(',', $subcat_ids).')
-  ;';
-    $image_ids_associated_outside = query2array($query, null, 'image_id');
-    $image_ids_not_orphan = array();
-
-    foreach ($image_ids_associated_outside as $image_id)
-    {
-      if (isset($image_ids_recursive_keys[$image_id]))
-      {
-        $image_ids_not_orphan[] = $image_id;
-      }
-    }
-
-    $category['nb_images_associated_outside'] = count(array_unique($image_ids_not_orphan));
-    $image_ids_becoming_orphan = array_diff($image_ids_recursive, $image_ids_not_orphan);
-    $category['nb_images_becoming_orphan'] = count($image_ids_becoming_orphan);
-  }
-}
-
-  $output[] = array(
-    'nb_images_associated_outside' => $category['nb_images_associated_outside'],
-    'nb_images_becoming_orphan' => $category['nb_images_becoming_orphan'],
-    'nb_images_recursive' => $category['nb_images_recursive'],
-  );
-  
-  return $output;
-}
-
 ?>
\ No newline at end of file
diff --git a/ws.php b/ws.php
index da00ffd2c..3e2e0daae 100644
--- a/ws.php
+++ b/ws.php
@@ -594,14 +594,14 @@ function ws_addDefaultMethods( $arr )
     );
 
   $service->addMethod(
-      'pwg.images.calculateOrphansOnAlbumDeletion',
-      'ws_images_calculateOrphansOnAlbumDeletion',
+      'pwg.categories.calculateOrphans',
+      'ws_categories_calculateOrphans',
       array(
         'category_id' =>  array('type'=>WS_TYPE_ID,
                                 'flags'=>WS_PARAM_FORCE_ARRAY),
         ),
       'Return the number of orphan photos if an album is deleted.',
-      $ws_functions_root . 'pwg.php',
+      $ws_functions_root . 'pwg.categories.php',
       array('admin_only'=>true)
     );