diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 2b852ad..15ef789 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -253,10 +253,10 @@ function _theme($hook, $variables = array()) {
       }
     }
     if (!$theme_registry->has($hook)) {
-      // Only trigger an error when not trying theme suggestions ($hook being an
+      // Only log a message when not trying theme suggestions ($hook being an
       // array).
       if (!isset($candidate)) {
-        trigger_error(sprintf("Theme hook %s not found.", $original_hook), E_USER_ERROR);
+        \Drupal::logger('theme')->warning('Theme hook %hook not found.', array('%hook' => $hook));
       }
       // There is no theme implementation for the hook passed. Return FALSE so
       // the function calling _theme() can differentiate between a hook that