diff --git a/transport/internet/kcp/xor.go b/transport/internet/kcp/xor.go
index b9f39f2bf..6de9d2953 100644
--- a/transport/internet/kcp/xor.go
+++ b/transport/internet/kcp/xor.go
@@ -1,3 +1,5 @@
+// +build !amd64
+
 package kcp
 
 // xorfwd performs XOR forwards in words, x[i] ^= x[i-4], i from 0 to len
diff --git a/transport/internet/kcp/xor_amd64.go b/transport/internet/kcp/xor_amd64.go
new file mode 100644
index 000000000..40d6a1be7
--- /dev/null
+++ b/transport/internet/kcp/xor_amd64.go
@@ -0,0 +1,4 @@
+package kcp
+
+func xorfwd(x []byte)
+func xorbkd(x []byte)