diff --git Solr_Base_Query.php Solr_Base_Query.php
index c555840..f331e9a 100644
--- Solr_Base_Query.php
+++ Solr_Base_Query.php
@@ -128,7 +128,8 @@ class Solr_Base_Query implements Drupal_Solr_Query_Interface {
     $this->filterstring = trim($filterstring);
     $this->parse_filters();
     $this->available_sorts = $this->default_sorts();
-    $this->parse_sortstring($sortstring);
+    $this->sortstring = trim($sortstring);
+    $this->parse_sortstring();
     $this->base_path = $base_path;
     $this->id = ++self::$idCount;
   }
@@ -236,9 +237,9 @@ class Solr_Base_Query implements Drupal_Solr_Query_Interface {
     $this->subqueries = array();
   }
 
-  protected function parse_sortstring($sortstring) {
+  protected function parse_sortstring($sortstring = NULL) {
     // Substitute any field aliases with real field names.
-    $sortstring = strtr(trim($sortstring), array_flip($this->field_map));
+    $sortstring = strtr($this->sortstring, array_flip($this->field_map));
     // Score is a special case - it's the default sort for Solr.
     if ('' == $sortstring) {
       $this->set_solrsort('score', 'asc');
@@ -270,10 +271,14 @@ class Solr_Base_Query implements Drupal_Solr_Query_Interface {
   public function set_available_sort($name, $sort) {
     // We expect non-aliased sorts to be added.
     $this->available_sorts[$name] = $sort;
+    // Re-parse the sortstring.
+    $this->parse_sortstring();
   }
 
   public function remove_available_sort($name) {
     unset($this->available_sorts[$name]);
+    // Re-parse the sortstring.
+    $this->parse_sortstring();
   }
 
   /**
diff --git apachesolr_search.module apachesolr_search.module
index 6700de8..4456607 100644
--- apachesolr_search.module
+++ apachesolr_search.module
@@ -207,6 +207,9 @@ function apachesolr_search_execute($keys, $filters, $solrsort, $base_path = '',
   apachesolr_search_add_facet_params($params, $query);
   apachesolr_search_add_boost_params($params, $query, $solr);
 
+  // Allow modules to alter the query prior to statically caching it.
+  // This can e.g. be used to add available sorts.
+  drupal_alter('apachesolr_current_query', $query);
 
   // Cache the built query. Since all the built queries go through
   // this process, all the hook_invocations will happen later