diff --git a/gtk2_ardour/processor_box.cc b/gtk2_ardour/processor_box.cc
index 91551e19bb..16088786cd 100644
--- a/gtk2_ardour/processor_box.cc
+++ b/gtk2_ardour/processor_box.cc
@@ -692,6 +692,7 @@ ProcessorBox::ProcessorBox (ARDOUR::Session* sess, boost::function<PluginSelecto
 	processor_display.set_flags (CAN_FOCUS);
 	processor_display.set_name ("ProcessorList");
 	processor_display.set_data ("processorbox", this);
+	processor_display.set_size_request (48, -1);
 	processor_display.set_spacing (2);
 
 	processor_display.signal_enter_notify_event().connect (sigc::mem_fun(*this, &ProcessorBox::enter_notify), false);