diff --git a/src/crypto/cipher/xor.go b/src/crypto/cipher/xor.go
index 020c9e1730..01ca0a9f08 100644
--- a/src/crypto/cipher/xor.go
+++ b/src/crypto/cipher/xor.go
@@ -10,7 +10,7 @@ import (
 )
 
 const wordSize = int(unsafe.Sizeof(uintptr(0)))
-const supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "amd64" || runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le"
+const supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "amd64" || runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" || runtime.GOARCH == "s390x"
 
 // fastXORBytes xors in bulk. It only works on architectures that
 // support unaligned read/writes.