diff --git biblio.module biblio.module
index 9080605..91b8362 100644
--- biblio.module
+++ biblio.module
@@ -2190,7 +2190,8 @@ function biblio_get_map($type, $format) {
     asort($fieldnames);
     $map = array_fill_keys($fieldnames, 1);
   }
- return $map;
+  drupal_alter('biblio_map', $map, $type, $format);
+  return $map;
 }
 
 function biblio_save_map($maps) {
diff --git modules/CiteProc/CSL.inc modules/CiteProc/CSL.inc
index 908a1ba..abd72dd 100644
--- modules/CiteProc/CSL.inc
+++ modules/CiteProc/CSL.inc
@@ -1713,14 +1713,6 @@ class csl_mapper {
   function map_field($field) {
     if (!isset($this->field_map)) {
       $this->field_map = biblio_get_map('field_map', 'csl');
-      $this->field_map = array_merge($this->field_map, array(
-          'author'                      => 'biblio_contributors:1',
-          'editor'                      => 'biblio_contributors:2',
-          'translator'                  => 'biblio_contributors:3',
-          'recipient'                   => ':',
-          'interviewer'                 => ':',
-          'composer'                    => ':',
-      ));
     }
 
     $vars = explode(' ', $field);
diff --git modules/CiteProc/biblio_citeproc.module modules/CiteProc/biblio_citeproc.module
index d93ae85..56f8f63 100644
--- modules/CiteProc/biblio_citeproc.module
+++ modules/CiteProc/biblio_citeproc.module
@@ -55,6 +55,22 @@ function biblio_citeproc_theme() {
   );
 }
 
+/**
+ * Implements hook_biblio_map_alter().
+ */
+function biblio_citeproc_biblio_map_alter(&$map, $type, $format) {
+  if ($type == 'field_map' && $format == 'csl') {
+    $map = array_merge($map, array(
+      'author'                      => 'biblio_contributors:1',
+      'editor'                      => 'biblio_contributors:2',
+      'translator'                  => 'biblio_contributors:3',
+      'recipient'                   => ':',
+      'interviewer'                 => ':',
+      'composer'                    => ':',
+    ));
+  }
+}
+
 function biblio_citeproc_theme_registry_alter(&$theme_registry) {
   $theme_registry['biblio_style'] = $theme_registry['biblio_citeproc_style'];
 }