diff -r b79a5ee173c4 libs/ardour/session.cc
--- a/libs/ardour/session.cc	Mon Dec 22 20:06:21 2008 +0000
+++ b/libs/ardour/session.cc	Mon Dec 22 20:54:34 2008 +0000
@@ -4018,8 +4018,7 @@
 		return result;
 	}
 
-	// any bigger than this seems to cause stack overflows in called functions
-	const nframes_t chunk_size = (128 * 1024)/4;
+	const nframes_t chunk_size = get_block_size ();
 
 	g_atomic_int_set (&processing_prohibited, 1);