diff --git a/gtk/gtkcssnode.c b/gtk/gtkcssnode.c
index 38d3eb03aa..bf4a5927ae 100644
--- a/gtk/gtkcssnode.c
+++ b/gtk/gtkcssnode.c
@@ -1052,8 +1052,8 @@ gtk_css_node_get_widget_type (GtkCssNode *cssnode)
 }
 
 void
-gtk_css_node_set_id (GtkCssNode *cssnode,
-                     const char *id)
+gtk_css_node_set_id (GtkCssNode                *cssnode,
+                     /* interned */ const char *id)
 {
   if (gtk_css_node_declaration_set_id (&cssnode->decl, id))
     {
@@ -1062,7 +1062,7 @@ gtk_css_node_set_id (GtkCssNode *cssnode,
     }
 }
 
-const char *
+/* interned */ const char *
 gtk_css_node_get_id (GtkCssNode *cssnode)
 {
   return gtk_css_node_declaration_get_id (cssnode->decl);
diff --git a/gtk/gtkcssnodeprivate.h b/gtk/gtkcssnodeprivate.h
index 2f9587ed17..7577d4808a 100644
--- a/gtk/gtkcssnodeprivate.h
+++ b/gtk/gtkcssnodeprivate.h
@@ -122,8 +122,8 @@ void                    gtk_css_node_set_widget_type    (GtkCssNode            *
                                                          GType                  widget_type);
 GType                   gtk_css_node_get_widget_type    (GtkCssNode            *cssnode);
 void                    gtk_css_node_set_id             (GtkCssNode            *cssnode,
-                                                         const char            *id);
-const char *            gtk_css_node_get_id             (GtkCssNode            *cssnode);
+                                                         /*interned*/const char*id);
+/*interned*/const char *gtk_css_node_get_id             (GtkCssNode            *cssnode);
 void                    gtk_css_node_set_state          (GtkCssNode            *cssnode,
                                                          GtkStateFlags          state_flags);
 GtkStateFlags           gtk_css_node_get_state          (GtkCssNode            *cssnode);