diff --git a/core/src/avm2/globals/flash/utils/ByteArray.as b/core/src/avm2/globals/flash/utils/ByteArray.as
index 76be70f78a93..0eb0d37492e4 100644
--- a/core/src/avm2/globals/flash/utils/ByteArray.as
+++ b/core/src/avm2/globals/flash/utils/ByteArray.as
@@ -1,6 +1,6 @@
 package flash.utils {
 	[Ruffle(InstanceAllocator)]
-	public class ByteArray implements IDataInput {
+	public class ByteArray implements IDataInput, IDataOutput {
 		private static var _defaultObjectEncoding:uint = 3;
 		public static function get defaultObjectEncoding():uint {
 			return _defaultObjectEncoding;
@@ -68,5 +68,9 @@ package flash.utils {
 		public native function writeUnsignedInt(value:uint):void;
 		public native function writeUTF(value:String):void;
 		public native function writeUTFBytes(value:String):void;
+		public function writeObject(object:*):void { 
+			// STUB
+			throw new Error("ByteArray.writeObject not implemented");
+		}
 	}
 }
diff --git a/core/src/avm2/globals/flash/utils/IDataOutput.as b/core/src/avm2/globals/flash/utils/IDataOutput.as
new file mode 100644
index 000000000000..e492e43809a4
--- /dev/null
+++ b/core/src/avm2/globals/flash/utils/IDataOutput.as
@@ -0,0 +1,22 @@
+package flash.utils {
+    public interface IDataOutput {
+        function get objectEncoding():uint;
+        function set objectEncoding(version:uint):void;
+
+        function get endian():String;
+        function set endian(type:String):void;
+
+        function writeBoolean(value:Boolean):void;
+        function writeByte(value:int):void;
+        function writeBytes(bytes:ByteArray, offset:uint = 0, length:uint = 0):void;
+        function writeDouble(value:Number):void;
+        function writeFloat(value:Number):void;
+        function writeInt(value:int):void;
+        function writeMultiByte(value:String, charSet:String):void;
+        function writeObject(object:*):void; // NOPMD WronglyNamedVariable
+        function writeShort(value:int):void;
+        function writeUnsignedInt(value:uint):void;
+        function writeUTF(value:String):void;
+        function writeUTFBytes(value:String):void;
+    }
+}
\ No newline at end of file
diff --git a/core/src/avm2/globals/globals.as b/core/src/avm2/globals/globals.as
index 5fb96c83c7ad..cd459eae891a 100644
--- a/core/src/avm2/globals/globals.as
+++ b/core/src/avm2/globals/globals.as
@@ -7,6 +7,7 @@ include "Math.as"
 include "flash/accessibility/AccessibilityProperties.as"
 include "flash/crypto.as"
 include "flash/utils/IDataInput.as"
+include "flash/utils/IDataOutput.as"
 include "flash/utils/ByteArray.as"
 include "flash/desktop/ClipboardFormats.as"
 include "flash/desktop/ClipboardTransferMode.as"