Index: wp-includes/user.php
===================================================================
--- wp-includes/user.php	(revision 18060)
+++ wp-includes/user.php	(working copy)
@@ -545,8 +545,10 @@
 			$this->results = $wpdb->get_col("SELECT $this->query_fields $this->query_from $this->query_where $this->query_orderby $this->query_limit");
 		}
 
-		if ( $this->query_vars['count_total'] )
-			$this->total_users = $wpdb->get_var("SELECT COUNT(*) $this->query_from $this->query_where");
+		if ( $this->query_vars['count_total'] ) {
+			$found_users_query = apply_filters( 'found_users_query', "SELECT COUNT(*) $this->query_from $this->query_where", $this );
+			$this->total_users = $wpdb->get_var( $found_users_query );
+		}
 
 		if ( !$this->results )
 			return;