diff --git a/modules/user/user.module b/modules/user/user.module
index d7e5ad56b266e00596d7720c4af5f6bef3ecb11b..c4d52b08129dbe68b70052e791612f4dbb3e5853 100644
--- a/modules/user/user.module
+++ b/modules/user/user.module
@@ -585,7 +585,7 @@ function user_block($op = 'list', $delta = 0, $edit = array()) {
           // Perform database queries to gather online user lists.  We use s.timestamp
           // rather than u.access because it is much faster is much faster..
           $anonymous_count = sess_count($interval);
-          $authenticated_users = db_query('SELECT u.uid, u.name FROM {users} u INNER JOIN {sessions} s ON u.uid = s.uid WHERE s.timestamp >= %d AND s.uid > 0 ORDER BY s.timestamp DESC', $interval);
+          $authenticated_users = db_query('SELECT DISTINCT u.uid, u.name FROM {users} u INNER JOIN {sessions} s ON u.uid = s.uid WHERE s.timestamp >= %d AND s.uid > 0 ORDER BY s.timestamp DESC', $interval);
           $authenticated_count = db_num_rows($authenticated_users);
 
           // Format the output with proper grammar.