diff --git a/gtk/css/gtkcssparser.c b/gtk/css/gtkcssparser.c
index d584ab70e4..f165a7b49d 100644
--- a/gtk/css/gtkcssparser.c
+++ b/gtk/css/gtkcssparser.c
@@ -812,6 +812,26 @@ gtk_css_parser_warn_syntax (GtkCssParser *self,
   va_end (args);
 }
 
+void
+gtk_css_parser_warn_deprecated (GtkCssParser *self,
+                                 const char   *format,
+                                 ...)
+{
+  va_list args;
+  GError *error;
+
+  va_start (args, format);
+  error = g_error_new_valist (GTK_CSS_PARSER_WARNING,
+                              GTK_CSS_PARSER_WARNING_DEPRECATED,
+                              format, args);
+  gtk_css_parser_emit_error (self,
+                             gtk_css_parser_get_start_location (self),
+                             gtk_css_parser_get_end_location (self),
+                             error);
+  g_error_free (error);
+  va_end (args);
+}
+
 gboolean
 gtk_css_parser_consume_function (GtkCssParser *self,
                                  guint         min_args,
diff --git a/gtk/css/gtkcssparserprivate.h b/gtk/css/gtkcssparserprivate.h
index d656f7c732..7e7ae11470 100644
--- a/gtk/css/gtkcssparserprivate.h
+++ b/gtk/css/gtkcssparserprivate.h
@@ -120,6 +120,9 @@ void                    gtk_css_parser_warn                     (GtkCssParser
 void                    gtk_css_parser_warn_syntax              (GtkCssParser                   *self,
                                                                  const char                     *format,
                                                                  ...) G_GNUC_PRINTF(2, 3);
+void                    gtk_css_parser_warn_deprecated          (GtkCssParser                   *self,
+                                                                 const char                     *format,
+                                                                 ...) G_GNUC_PRINTF(2, 3);
 
 
 gboolean                gtk_css_parser_has_token                (GtkCssParser                   *self,