diff --git a/libs/ardour/ardour/chan_mapping.h b/libs/ardour/ardour/chan_mapping.h
index ebb7be402a..7b9f81976d 100644
--- a/libs/ardour/ardour/chan_mapping.h
+++ b/libs/ardour/ardour/chan_mapping.h
@@ -40,6 +40,7 @@ public:
 	ChanMapping(ARDOUR::ChanCount identity);
 
 	uint32_t get(DataType t, uint32_t from, bool* valid);
+	uint32_t get(DataType t, uint32_t from) { return get (t, from, NULL); }
 	void     set(DataType t, uint32_t from, uint32_t to);
 	void     offset_from(DataType t, int32_t delta);
 	void     offset_to(DataType t, int32_t delta);
diff --git a/libs/ardour/chan_mapping.cc b/libs/ardour/chan_mapping.cc
index 5c5bb17de6..57734803d2 100644
--- a/libs/ardour/chan_mapping.cc
+++ b/libs/ardour/chan_mapping.cc
@@ -45,15 +45,15 @@ ChanMapping::get(DataType t, uint32_t from, bool* valid)
 {
 	Mappings::iterator tm = _mappings.find(t);
 	if (tm == _mappings.end()) {
-		*valid = false;
+		if (valid) { *valid = false; }
 		return -1;
 	}
 	TypeMapping::iterator m = tm->second.find(from);
 	if (m == tm->second.end()) {
-		*valid = false;
+		if (valid) { *valid = false; }
 		return -1;
 	}
-	*valid = true;
+	if (valid) { *valid = true; }
 	return m->second;
 }