diff --git a/libs/ardour/ardour/audiofilesource.h b/libs/ardour/ardour/audiofilesource.h
index 7688fc7872..c5fd7b3af2 100644
--- a/libs/ardour/ardour/audiofilesource.h
+++ b/libs/ardour/ardour/audiofilesource.h
@@ -112,7 +112,8 @@ protected:
 	static char bwf_organization_code[4];
 	static char bwf_serial_number[13];
 
-	static uint64_t header_position_offset;
+	/** Kept up to date with the position of the session location start */
+	static framecnt_t header_position_offset;
 
   private:
 	std::string old_peak_path (std::string audio_path);
diff --git a/libs/ardour/audiofilesource.cc b/libs/ardour/audiofilesource.cc
index 7b88762a41..3ae0db2101 100644
--- a/libs/ardour/audiofilesource.cc
+++ b/libs/ardour/audiofilesource.cc
@@ -71,7 +71,7 @@ using namespace Glib;
 string AudioFileSource::peak_dir = "";
 
 PBD::Signal0<void> AudioFileSource::HeaderPositionOffsetChanged;
-uint64_t           AudioFileSource::header_position_offset = 0;
+framecnt_t         AudioFileSource::header_position_offset = 0;
 
 /* XXX maybe this too */
 char AudioFileSource::bwf_serial_number[13] = "000000000000";