diff --git a/subpathauto.module b/subpathauto.module
index 4fd2eda..bf1d27c 100644
--- a/subpathauto.module
+++ b/subpathauto.module
@@ -131,9 +131,14 @@ function subpathauto_lookup_subpath($action, $path = '', $original_path, $path_l
     }
     elseif ($action == 'source' && $sourced_base_path = drupal_lookup_path('source', $base_path, $path_language)) {
       if ($sourced_base_path != $base_path) {
-        $source = $sourced_base_path . '/' . implode('/', $path_suffix);
-        //subpathauto_cache_subpath_alias($source, $path, $path_language);
-        return $source;
+        //$source = $sourced_base_path . '/' . implode('/', $path_suffix);
+        $source = $base_path . '/' . implode('/', $path_suffix);
+
+        if(!drupal_valid_path($source)) {
+          return FALSE;
+        } else {
+          return $source;
+        }
       }
     }
   }