diff --git a/src/pkg/crypto/sha1/sha1block_decl.go b/src/pkg/crypto/sha1/sha1block_decl.go
index 2331deb3a9..24e521af1f 100644
--- a/src/pkg/crypto/sha1/sha1block_decl.go
+++ b/src/pkg/crypto/sha1/sha1block_decl.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build amd64 amd64p32 386
+// +build amd64 amd64p32 arm 386
 
 package sha1