diff --git a/arm/armspec/spec.go b/arm/armspec/spec.go
index e02d092..274f0e0 100644
--- a/arm/armspec/spec.go
+++ b/arm/armspec/spec.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build go1.6
 // +build !386 go1.8
 // ... see golang.org/issue/12840
 
diff --git a/vendor/rsc.io/pdf/lex.go b/vendor/rsc.io/pdf/lex.go
index 85bfdcc..0a7e335 100644
--- a/vendor/rsc.io/pdf/lex.go
+++ b/vendor/rsc.io/pdf/lex.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build go1.6
 // +build !386 go1.8
 // ... see golang.org/issue/12840
 
diff --git a/vendor/rsc.io/pdf/page.go b/vendor/rsc.io/pdf/page.go
index 6669907..7ce5f48 100644
--- a/vendor/rsc.io/pdf/page.go
+++ b/vendor/rsc.io/pdf/page.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build go1.6
 // +build !386 go1.8
 // ... see golang.org/issue/12840
 
diff --git a/vendor/rsc.io/pdf/ps.go b/vendor/rsc.io/pdf/ps.go
index 69292aa..8c829f0 100644
--- a/vendor/rsc.io/pdf/ps.go
+++ b/vendor/rsc.io/pdf/ps.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build go1.6
 // +build !386 go1.8
 // ... see golang.org/issue/12840
 
diff --git a/vendor/rsc.io/pdf/read.go b/vendor/rsc.io/pdf/read.go
index 84cb17a..4d67c14 100644
--- a/vendor/rsc.io/pdf/read.go
+++ b/vendor/rsc.io/pdf/read.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build go1.6
 // +build !386 go1.8
 // ... see golang.org/issue/12840