diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 2af07a2..ee77ffa 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -380,7 +380,7 @@ function _theme($hook, $variables = array()) {
     if (function_exists($info['function'])) {
       $output = SafeMarkup::set($info['function']($variables));
     }
-    else {
+    elseif (!isset($info['render element'])) {
       // The function is registered but does not exist (yet).
       trigger_error(sprintf("Missing theme function '%s' for theme hook '%s'. Either rebuild the theme registry and/or correct the definition.", $info['function'], $hook), E_USER_WARNING);
     }