diff --git a/libs/ardour/ardour/types.h b/libs/ardour/ardour/types.h
index 8dc4ce55e4..03695bcb9e 100644
--- a/libs/ardour/ardour/types.h
+++ b/libs/ardour/ardour/types.h
@@ -261,8 +261,8 @@ namespace ARDOUR {
 
 };
 
-std::istream& operator>>(std::istream& o, ARDOUR::SampleFormat sf);
-std::istream& operator>>(std::istream& o, ARDOUR::HeaderFormat sf);
+std::istream& operator>>(std::istream& o, ARDOUR::SampleFormat& sf);
+std::istream& operator>>(std::istream& o, ARDOUR::HeaderFormat& sf);
 
 static inline jack_nframes_t
 session_frame_to_track_frame (jack_nframes_t session_frame, double speed)
diff --git a/libs/ardour/globals.cc b/libs/ardour/globals.cc
index eb46943a43..4879e373d5 100644
--- a/libs/ardour/globals.cc
+++ b/libs/ardour/globals.cc
@@ -546,14 +546,14 @@ ARDOUR::coverage (jack_nframes_t sa, jack_nframes_t ea,
 
 /* not sure where to put these */
 
-std::istream& operator>>(std::istream& o, HeaderFormat hf) {
+std::istream& operator>>(std::istream& o, HeaderFormat& hf) {
 	int val;
 	o >> val;
 	hf = (HeaderFormat) val;
 	return o;
 }
 
-std::istream& operator>>(std::istream& o, SampleFormat sf) {
+std::istream& operator>>(std::istream& o, SampleFormat& sf) {
 	int val;
 	o >> val;
 	sf = (SampleFormat) val;