diff --git a/gtk/tools/gtk-builder-tool-simplify.c b/gtk/tools/gtk-builder-tool-simplify.c
index 3cd917f2cd..06689ce9c5 100644
--- a/gtk/tools/gtk-builder-tool-simplify.c
+++ b/gtk/tools/gtk-builder-tool-simplify.c
@@ -449,6 +449,9 @@ value_is_default (Element      *element,
   if (g_type_is_a (G_PARAM_SPEC_VALUE_TYPE (pspec), G_TYPE_OBJECT))
     return FALSE;
 
+  if (g_type_is_a (G_PARAM_SPEC_VALUE_TYPE (pspec), G_TYPE_BOXED))
+    return FALSE;
+
   if (!gtk_builder_value_from_string (data->builder, pspec, value_string, &value, &error))
     {
       g_printerr (_("%s:%d: Couldn’t parse value for property '%s': %s\n"), data->input_filename, element->line_number, pspec->name, error->message);