diff --git a/ipv6/zsys_dragonfly.go b/ipv6/zsys_dragonfly.go
index ae18955b..5a03ab73 100644
--- a/ipv6/zsys_dragonfly.go
+++ b/ipv6/zsys_dragonfly.go
@@ -1,6 +1,8 @@
 // Created by cgo -godefs - DO NOT EDIT
 // cgo -godefs defs_dragonfly.go
 
+// +build dragonfly
+
 package ipv6
 
 const (
diff --git a/ipv6/zsys_solaris.go b/ipv6/zsys_solaris.go
index 3407bf84..cdf00c25 100644
--- a/ipv6/zsys_solaris.go
+++ b/ipv6/zsys_solaris.go
@@ -1,6 +1,8 @@
 // Created by cgo -godefs - DO NOT EDIT
 // cgo -godefs defs_solaris.go
 
+// +build solaris
+
 package ipv6
 
 const (