diff --git a/cmd/syncthing/memsize_solaris.go b/cmd/syncthing/memsize_solaris.go
index 360b5e1ad..9273879e9 100644
--- a/cmd/syncthing/memsize_solaris.go
+++ b/cmd/syncthing/memsize_solaris.go
@@ -1,3 +1,5 @@
+// +build solaris
+
 package main
 
 import (