diff --git a/libs/ardour/sndfilesource.cc b/libs/ardour/sndfilesource.cc
index 58fbab233b..618cfac783 100644
--- a/libs/ardour/sndfilesource.cc
+++ b/libs/ardour/sndfilesource.cc
@@ -463,7 +463,7 @@ SndFileSource::nondestructive_write_unlocked (Sample *data, framecnt_t cnt)
 		return 0;
 	}
 
-	int32_t frame_pos = _length;
+	framepos_t frame_pos = _length;
 
 	if (write_float (data, frame_pos, cnt) != cnt) {
 		return 0;