diff --git a/libs/ardour/ardour/chan_mapping.h b/libs/ardour/ardour/chan_mapping.h
index f1ffef373e..ac546e3bbd 100644
--- a/libs/ardour/ardour/chan_mapping.h
+++ b/libs/ardour/ardour/chan_mapping.h
@@ -88,7 +88,9 @@ public:
 	 */
 	bool     is_monotonic () const;
 
-	uint32_t count () const;
+	uint32_t n_total () const;
+
+	ChanCount count () const;
 
 	XMLNode* state(const std::string& name) const;
 
diff --git a/libs/ardour/chan_mapping.cc b/libs/ardour/chan_mapping.cc
index 1d59faff00..ca422b5bce 100644
--- a/libs/ardour/chan_mapping.cc
+++ b/libs/ardour/chan_mapping.cc
@@ -219,8 +219,9 @@ ChanMapping::is_identity (ChanCount offset) const
 }
 
 uint32_t
-ChanMapping::count () const
+ChanMapping::n_total () const
 {
+	// fast version of count().n_total();
 	uint32_t rv = 0;
 	const Mappings& mp (mappings());
 	for (Mappings::const_iterator tm = mp.begin(); tm != mp.end(); ++tm) {
@@ -229,6 +230,19 @@ ChanMapping::count () const
 	return rv;
 }
 
+ChanCount
+ChanMapping::count () const
+{
+	ChanCount rv;
+	const Mappings& mp (mappings());
+	for (Mappings::const_iterator tm = mp.begin(); tm != mp.end(); ++tm) {
+		rv.set (tm->first, tm->second.size ());
+	}
+	return rv;
+}
+
+
+
 } // namespace ARDOUR
 
 std::ostream& operator<<(std::ostream& o, const ARDOUR::ChanMapping& cm)
diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index bda00f59d3..55b592561c 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -1073,7 +1073,7 @@ PluginInsert::check_inplace ()
 {
 	bool inplace_ok = !_plugins.front()->inplace_broken ();
 
-	if (_thru_map.count () > 0) {
+	if (_thru_map.n_total () > 0) {
 		// TODO once midi-bypass is part of the mapping, ignore it
 		inplace_ok = false;
 	}