diff --git a/gtk2_ardour/plugin_ui.cc b/gtk2_ardour/plugin_ui.cc
index d0980b0df6..0524ebb235 100644
--- a/gtk2_ardour/plugin_ui.cc
+++ b/gtk2_ardour/plugin_ui.cc
@@ -173,6 +173,7 @@ PluginUIWindow::PluginUIWindow (
 		if (h > 600) h = 600;
 	}
 
+	set_border_width (0);
 	set_default_size (w, h);
 	set_resizable (_pluginui->resizable());
 }