diff --git a/writer_tinygo.go b/writer_tinygo.go
new file mode 100644
index 0000000..3b06e99
--- /dev/null
+++ b/writer_tinygo.go
@@ -0,0 +1,18 @@
+// +build tinygo
+
+package fwd
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// unsafe cast string as []byte
+func unsafestr(b string) []byte {
+	l := uintptr(len(b))
+	return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
+		Len:  l,
+		Cap:  l,
+		Data: (*reflect.StringHeader)(unsafe.Pointer(&b)).Data,
+	}))
+}
diff --git a/writer_unsafe.go b/writer_unsafe.go
index a0bf453..1701572 100644
--- a/writer_unsafe.go
+++ b/writer_unsafe.go
@@ -1,4 +1,4 @@
-// +build !appengine
+// +build !appengine,!tinygo
 
 package fwd