diff --git a/src/commonMain/kotlin/Codec.kt b/src/commonMain/kotlin/Codec.kt
index 22aa676..c072ef3 100644
--- a/src/commonMain/kotlin/Codec.kt
+++ b/src/commonMain/kotlin/Codec.kt
@@ -2,6 +2,7 @@ package cz.smarteon.loxone
 
 import com.ditchoom.buffer.ByteOrder
 import com.ditchoom.buffer.PlatformBuffer
+import com.ditchoom.buffer.allocate
 import com.ditchoom.buffer.wrap
 import cz.smarteon.loxone.message.MessageHeader
 import cz.smarteon.loxone.message.MessageHeader.Companion.FIRST_BYTE
@@ -56,4 +57,13 @@ object Codec {
             )
         }
     }
+
+    internal fun writeHeader(header: MessageHeader): ByteArray {
+        val buffer = PlatformBuffer.allocate(PAYLOAD_LENGTH, byteOrder = ByteOrder.LITTLE_ENDIAN)
+        buffer[0] = FIRST_BYTE
+        buffer[1] = header.kind.ordinal.toByte()
+        buffer[2] = (if (header.sizeEstimated) 1 else 0).toByte()
+        buffer[MSG_SIZE_POSITION] = header.messageSize.toUInt()
+        return buffer.readByteArray(PAYLOAD_LENGTH)
+    }
 }
diff --git a/src/commonTest/kotlin/CodecTest.kt b/src/commonTest/kotlin/CodecTest.kt
index cb2edbf..48dbf64 100644
--- a/src/commonTest/kotlin/CodecTest.kt
+++ b/src/commonTest/kotlin/CodecTest.kt
@@ -20,4 +20,9 @@ class CodecTest : StringSpec({
         val header = Codec.readHeader(Codec.hexToBytes("03000000ab000000"))
         header shouldBe MessageHeader(MessageKind.TEXT, false, 171)
     }
+
+    "should write header" {
+        val header = MessageHeader(MessageKind.TEXT, false, 171)
+        Codec.writeHeader(header) shouldBe Codec.hexToBytes("03000000ab000000")
+    }
 })