diff --git a/gtk/gtkheaderbar.c b/gtk/gtkheaderbar.c
index 42a2300810..dcdcb4f4fd 100644
--- a/gtk/gtkheaderbar.c
+++ b/gtk/gtkheaderbar.c
@@ -2045,6 +2045,7 @@ gtk_header_bar_set_decoration_layout (GtkHeaderBar *bar,
 
   priv = gtk_header_bar_get_instance_private (bar);
 
+  g_free (priv->decoration_layout);
   priv->decoration_layout = g_strdup (layout);
   priv->decoration_layout_set = (layout != NULL);