diff --git a/gtk2_ardour/ardour_button.cc b/gtk2_ardour/ardour_button.cc
index 942d678bfb..1d98a7b84f 100644
--- a/gtk2_ardour/ardour_button.cc
+++ b/gtk2_ardour/ardour_button.cc
@@ -75,10 +75,12 @@ ArdourButton::ArdourButton (Element e)
 
 ArdourButton::ArdourButton (const std::string& str, Element e)
 	: _elements (e)
+	, _tweaks (Tweaks (0))
 	, _text_width (0)
 	, _text_height (0)
 	, _diameter (11.0)
 	, _corner_radius (9.0)
+	, _corner_mask (0xf)
 	, edge_pattern (0)
 	, active_pattern (0)
 	, inactive_pattern (0)