diff --git a/core/src/main/kotlin/ch/dissem/bitmessage/entity/GetData.kt b/core/src/main/kotlin/ch/dissem/bitmessage/entity/GetData.kt
index 455b663..570f74e 100644
--- a/core/src/main/kotlin/ch/dissem/bitmessage/entity/GetData.kt
+++ b/core/src/main/kotlin/ch/dissem/bitmessage/entity/GetData.kt
@@ -17,9 +17,6 @@
 package ch.dissem.bitmessage.entity
 
 import ch.dissem.bitmessage.entity.valueobject.InventoryVector
-import ch.dissem.bitmessage.utils.Encode
-import java.io.OutputStream
-import java.nio.ByteBuffer
 
 /**
  * The 'getdata' command is used to request objects from a node.
@@ -31,24 +28,8 @@ class GetData constructor(var inventory: List<InventoryVector>) : MessagePayload
     override fun writer(): StreamableWriter = Writer(this)
 
     private class Writer(
-        private val item: GetData
-    ) : StreamableWriter {
-
-        override fun write(out: OutputStream) {
-            Encode.varInt(item.inventory.size, out)
-            for (iv in item.inventory) {
-                iv.writer().write(out)
-            }
-        }
-
-        override fun write(buffer: ByteBuffer) {
-            Encode.varInt(item.inventory.size, buffer)
-            for (iv in item.inventory) {
-                iv.writer().write(buffer)
-            }
-        }
-
-    }
+        item: GetData
+    ) : InventoryWriter(item.inventory)
 
     companion object {
         @JvmField
diff --git a/core/src/main/kotlin/ch/dissem/bitmessage/entity/Inv.kt b/core/src/main/kotlin/ch/dissem/bitmessage/entity/Inv.kt
index beb2e85..65d201e 100644
--- a/core/src/main/kotlin/ch/dissem/bitmessage/entity/Inv.kt
+++ b/core/src/main/kotlin/ch/dissem/bitmessage/entity/Inv.kt
@@ -17,9 +17,6 @@
 package ch.dissem.bitmessage.entity
 
 import ch.dissem.bitmessage.entity.valueobject.InventoryVector
-import ch.dissem.bitmessage.utils.Encode
-import java.io.OutputStream
-import java.nio.ByteBuffer
 
 /**
  * The 'inv' command holds up to 50000 inventory vectors, i.e. hashes of inventory items.
@@ -31,22 +28,6 @@ class Inv constructor(val inventory: List<InventoryVector>) : MessagePayload {
     override fun writer(): StreamableWriter = Writer(this)
 
     private class Writer(
-        private val item: Inv
-    ) : StreamableWriter {
-
-        override fun write(out: OutputStream) {
-            Encode.varInt(item.inventory.size, out)
-            for (iv in item.inventory) {
-                iv.writer().write(out)
-            }
-        }
-
-        override fun write(buffer: ByteBuffer) {
-            Encode.varInt(item.inventory.size, buffer)
-            for (iv in item.inventory) {
-                iv.writer().write(buffer)
-            }
-        }
-
-    }
+        item: Inv
+    ) : InventoryWriter(item.inventory)
 }
diff --git a/core/src/main/kotlin/ch/dissem/bitmessage/entity/InventoryWriter.kt b/core/src/main/kotlin/ch/dissem/bitmessage/entity/InventoryWriter.kt
new file mode 100644
index 0000000..6ed5808
--- /dev/null
+++ b/core/src/main/kotlin/ch/dissem/bitmessage/entity/InventoryWriter.kt
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2018 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.entity
+
+import ch.dissem.bitmessage.entity.valueobject.InventoryVector
+import ch.dissem.bitmessage.utils.Encode
+import java.io.OutputStream
+import java.nio.ByteBuffer
+
+internal open class InventoryWriter(private val inventory: List<InventoryVector>) : StreamableWriter {
+
+    override fun write(out: OutputStream) {
+        Encode.varInt(inventory.size, out)
+        for (iv in inventory) {
+            iv.writer().write(out)
+        }
+    }
+
+    override fun write(buffer: ByteBuffer) {
+        Encode.varInt(inventory.size, buffer)
+        for (iv in inventory) {
+            iv.writer().write(buffer)
+        }
+    }
+
+}