Index: libs/ardour/sndfilesource.cc
===================================================================
--- libs/ardour/sndfilesource.cc        (revision 1065)
+++ libs/ardour/sndfilesource.cc        (working copy)
@@ -213,7 +213,9 @@
        if (destructive()) {
                xfade_buf = new Sample[xfade_frames];
                timeline_position = header_position_offset;
-       }
+       } else {
+               xfade_buf = NULL;
+       }

        AudioFileSource::HeaderPositionOffsetChanged.connect (mem_fun (*this, &SndFileSource::handle_header_position_change));
 }