diff --git a/gtk/gtkstylecontext.c b/gtk/gtkstylecontext.c
index 9a5587d51c..9176c02741 100644
--- a/gtk/gtkstylecontext.c
+++ b/gtk/gtkstylecontext.c
@@ -1402,9 +1402,9 @@ gtk_style_context_list_classes (GtkStyleContext *context)
   
   classes = gtk_css_node_list_classes (priv->cssnode, &n_classes);
 
-  for (i = n_classes; i-- > n_classes;)
+  for (i = n_classes; i > 0; i--)
     {
-      quark_str = g_quark_to_string (classes[i]);
+      quark_str = g_quark_to_string (classes[i - 1]);
       classes_list = g_list_prepend (classes_list, (gchar *) quark_str);
     }