diff --git a/libs/ardour/ardour/presentation_info.h b/libs/ardour/ardour/presentation_info.h
index 8e55ccee04..3949ef3787 100644
--- a/libs/ardour/ardour/presentation_info.h
+++ b/libs/ardour/ardour/presentation_info.h
@@ -294,6 +294,8 @@ class LIBARDOUR_API PresentationInfo : public PBD::Stateful
 
 }
 
+namespace std {
 std::ostream& operator<<(std::ostream& o, ARDOUR::PresentationInfo const& rid);
+}
 
 #endif /* __libardour_presentation_info_h__ */
diff --git a/libs/ardour/presentation_info.cc b/libs/ardour/presentation_info.cc
index 37d6e115f3..3d8a4ee271 100644
--- a/libs/ardour/presentation_info.cc
+++ b/libs/ardour/presentation_info.cc
@@ -318,7 +318,7 @@ PresentationInfo::operator= (PresentationInfo const& other)
 }
 
 std::ostream&
-operator<<(std::ostream& o, ARDOUR::PresentationInfo const& pi)
+std::operator<<(std::ostream& o, ARDOUR::PresentationInfo const& pi)
 {
 	return o << pi.order() << '/' << enum_2_string (pi.flags()) << '/' << pi.color();
 }