diff --git a/libs/ardour/ardour/audiofilesource.h b/libs/ardour/ardour/audiofilesource.h
index d91280284d..b833ee1807 100644
--- a/libs/ardour/ardour/audiofilesource.h
+++ b/libs/ardour/ardour/audiofilesource.h
@@ -88,7 +88,7 @@ protected:
 			SampleFormat samp_format, HeaderFormat hdr_format);
 
 	/** Constructor to be called for existing in-session files */
-	AudioFileSource (Session&, const XMLNode&, bool must_exist = true);
+	AudioFileSource (Session&, const XMLNode&, bool must_exist = true, bool optional_origin = false);
 
 	/** Constructor to be called for crash recovery. Final argument is not
 	 * used but exists to differentiate from the external-to-session
diff --git a/libs/ardour/ardour/silentfilesource.h b/libs/ardour/ardour/silentfilesource.h
index 80f4b361b2..ebc295d08d 100644
--- a/libs/ardour/ardour/silentfilesource.h
+++ b/libs/ardour/ardour/silentfilesource.h
@@ -45,7 +45,7 @@ protected:
 
 	SilentFileSource (Session& s, const XMLNode& x, framecnt_t len, float srate)
 		: Source (s, x)
-		, AudioFileSource (s, x, false)
+		, AudioFileSource (s, x, false, true)
 		, _sample_rate(srate)
 	{
 		_length = len;
diff --git a/libs/ardour/audiofilesource.cc b/libs/ardour/audiofilesource.cc
index a25e19ea5a..8e1f50a55d 100644
--- a/libs/ardour/audiofilesource.cc
+++ b/libs/ardour/audiofilesource.cc
@@ -135,7 +135,7 @@ AudioFileSource::AudioFileSource (Session& s, const string& path, Source::Flag f
  * is an absolute path after ::set_state(), then the file is external to the
  * session.
  */
-AudioFileSource::AudioFileSource (Session& s, const XMLNode& node, bool must_exist)
+AudioFileSource::AudioFileSource (Session& s, const XMLNode& node, bool must_exist, bool optional_origin)
 	: Source (s, node)
 	, AudioSource (s, node)
 	, FileSource (s, node, must_exist)
@@ -146,7 +146,7 @@ AudioFileSource::AudioFileSource (Session& s, const XMLNode& node, bool must_exi
 
 	if (Glib::path_is_absolute (_origin)) {
 		_path = _origin;
-		must_exist = true;
+		must_exist = !optional_origin;
 	}
 
 	if (init (_path, must_exist)) {