diff --git a/modules/path/path.module b/modules/path/path.module
index 4614b0f..66dc495 100644
--- a/modules/path/path.module
+++ b/modules/path/path.module
@@ -173,10 +173,10 @@ function path_form_element_validate($element, &$form_state, $complete_form) {
     if (!empty($path['source'])) {
       $query->condition('source', $path['source'], '<>');
     }
-    $query->addExpression('1');
+    $query->addField('url_alias', 'source');
     $query->range(0, 1);
-    if ($query->execute()->fetchField()) {
-      form_error($element, t('The alias is already in use.'));
+    if ($existing_source = $query->execute()->fetchField()) {
+      form_error($element, t('The alias is already in use by %existing', array('%existing' => $existing_source)));
     }
   }
 }