diff --git a/libs/pbd/pbd/natsort.h b/libs/pbd/pbd/natsort.h
index c50a6f288b..31c1dd7bcd 100644
--- a/libs/pbd/pbd/natsort.h
+++ b/libs/pbd/pbd/natsort.h
@@ -24,7 +24,7 @@
 
 namespace PBD {
 
-bool
+inline bool
 naturally_less (const char* a, const char* b)
 {
 	const char* d_a = NULL;