diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index d9f6fa4662..ac521fbd4c 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -20,6 +20,11 @@
 #ifndef __ardour_audioengine_h__
 #define __ardour_audioengine_h__
 
+#ifdef WAF_BUILD
+#include "libardour-config.h"
+#endif
+
+#include <iostream>
 #include <list>
 #include <set>
 #include <cmath>
diff --git a/libs/ardour/io.cc b/libs/ardour/io.cc
index 29659a2d0c..98484c22de 100644
--- a/libs/ardour/io.cc
+++ b/libs/ardour/io.cc
@@ -59,7 +59,7 @@ extern "C" int isnan (double);
 extern "C" int isinf (double);
 #endif
 
-#define BLOCK_PROCESS_CALLBACK() Glib::Mutex::Lock em (_session.engine().process_lock())
+#define BLOCK_PROCESS_CALLBACK() Glib::Mutex::Lock em (AudioEngine::instance()->process_lock())
 
 using namespace std;
 using namespace ARDOUR;