diff --git a/libs/temporal/tempo.cc b/libs/temporal/tempo.cc
index 32f9913f47..91dcfcd6f5 100644
--- a/libs/temporal/tempo.cc
+++ b/libs/temporal/tempo.cc
@@ -3112,6 +3112,12 @@ TempoMap::init ()
 	fetch ();
 }
 
+TempoMap::SharedPtr
+TempoMap::write_copy()
+{
+	return _map_mgr.write_copy();
+}
+
 int
 TempoMap::update (TempoMap::SharedPtr m)
 {
diff --git a/libs/temporal/temporal/tempo.h b/libs/temporal/temporal/tempo.h
index 4d251d9f6d..52daf2e37e 100644
--- a/libs/temporal/temporal/tempo.h
+++ b/libs/temporal/temporal/tempo.h
@@ -653,7 +653,7 @@ class LIBTEMPORAL_API TempoMap : public PBD::StatefulDestructible
 	static SharedPtr use() { assert (_tempo_map_p); return _tempo_map_p; }
 	static SharedPtr fetch() { update_thread_tempo_map(); return use(); }
 
-	static SharedPtr write_copy() { return _map_mgr.write_copy(); }
+	static SharedPtr write_copy();
 	static void fetch_writable() { _tempo_map_p = write_copy(); }
 	static int  update (SharedPtr m);
 	static void abort_update ();