diff --git a/browser/lib/util/bufferutils.js b/browser/lib/util/bufferutils.js
index 1f4a0a647e..0e8747d1f1 100644
--- a/browser/lib/util/bufferutils.js
+++ b/browser/lib/util/bufferutils.js
@@ -5,11 +5,6 @@ var BufferUtils = (function() {
 
 	function isWordArray(ob) { return ob !== null && ob !== undefined && ob.sigBytes !== undefined; }
 	function isArrayBuffer(ob) { return ob !== null && ob !== undefined && ob.constructor === ArrayBuffer; }
-	// msgpack.decode for raw binary data gives a wordArray-like object that isn't a proper wordArray,
-	// so doesn't have a wordArray.clamp() method
-	function ensureProperWordArray(wordArray) {
-		return (wordArray.clamp !== undefined ? wordArray : WordArray.create(wordArray.words));
-	}
 
 	// https://gist.githubusercontent.com/jonleighton/958841/raw/f200e30dfe95212c0165ccf1ae000ca51e9de803/gistfile1.js
 	function arrayBufferToBase64(ArrayBuffer) {
@@ -81,6 +76,29 @@ var BufferUtils = (function() {
 
 	BufferUtils.isBuffer = function(buf) { return isArrayBuffer(buf) || isWordArray(buf); };
 
+	BufferUtils.toArrayBuffer = function(buf) {
+		if(!ArrayBuffer)
+			throw new Error("Can't convert to ArrayBuffer: ArrayBuffer not supported");
+
+		if(isArrayBuffer(buf))
+			return buf;
+
+		if(isWordArray(buf)) {
+			/* Backported from unreleased CryptoJS
+			* https://code.google.com/p/crypto-js/source/browse/branches/3.x/src/lib-typedarrays.js?r=661 */
+			var arrayBuffer = new ArrayBuffer(buf.sigBytes);
+			var uint8View = new Uint8Array(arrayBuffer);
+
+			for (var i = 0; i < buf.sigBytes; i++) {
+				uint8View[i] = (buf.words[i >>> 2] >>> (24 - (i % 4) * 8)) & 0xff;
+			}
+
+			return arrayBuffer;
+		};
+
+		throw new Error("BufferUtils.toArrayBuffer expected a buffer");
+	};
+
 	BufferUtils.toWordArray = function(buf) {
 		return isWordArray(buf) ? buf : WordArray.create(buf);
 	};
@@ -89,7 +107,7 @@ var BufferUtils = (function() {
 		if(isArrayBuffer(buf))
 			return arrayBufferToBase64(buf);
 		if(isWordArray(buf))
-			return CryptoJS.enc.Base64.stringify(ensureProperWordArray(buf));
+			return CryptoJS.enc.Base64.stringify(buf);
 	};
 
 	BufferUtils.base64Decode = function(str) {
diff --git a/common/lib/types/message.js b/common/lib/types/message.js
index 7ace95aa90..2dbac29c06 100644
--- a/common/lib/types/message.js
+++ b/common/lib/types/message.js
@@ -27,10 +27,17 @@ var Message = (function() {
 		 * although msgpack calls toJSON(), we know it is a stringify()
 		 * call if it has a non-empty arguments list */
 		var data = this.data;
-		if(data && arguments.length > 0 && BufferUtils.isBuffer(data)) {
-			var encoding = this.encoding;
-			result.encoding = encoding ? (encoding + '/base64') : 'base64';
-			data = BufferUtils.base64Encode(data);
+		if(data && BufferUtils.isBuffer(data)) {
+			if(arguments.length > 0) {
+				/* stringify call */
+				var encoding = this.encoding;
+				result.encoding = encoding ? (encoding + '/base64') : 'base64';
+				data = BufferUtils.base64Encode(data);
+			} else {
+				/* Called by msgpack. Need to feed it an ArrayBuffer, msgpack doesn't
+				* understand WordArrays */
+				data = BufferUtils.toArrayBuffer(data);
+			}
 		}
 		result.data = data;
 		return result;
diff --git a/common/lib/types/presencemessage.js b/common/lib/types/presencemessage.js
index c435d1e001..e0a99551bb 100644
--- a/common/lib/types/presencemessage.js
+++ b/common/lib/types/presencemessage.js
@@ -30,14 +30,21 @@ var PresenceMessage = (function() {
 			encoding: this.encoding
 		};
 
-		/* encode to base64 if we're returning real JSON;
+		/* encode data to base64 if present and we're returning real JSON;
 		 * although msgpack calls toJSON(), we know it is a stringify()
-		 * call if it passes on the stringify arguments */
+		 * call if it has a non-empty arguments list */
 		var data = this.data;
-		if(data && arguments.length > 0 && BufferUtils.isBuffer(data)) {
-			var encoding = this.encoding;
-			result.encoding = encoding ? (encoding + '/base64') : 'base64';
-			data = data.toString('base64');
+		if(data && BufferUtils.isBuffer(data)) {
+			if(arguments.length > 0) {
+				/* stringify call */
+				var encoding = this.encoding;
+				result.encoding = encoding ? (encoding + '/base64') : 'base64';
+				data = BufferUtils.base64Encode(data);
+			} else {
+				/* Called by msgpack. Need to feed it an ArrayBuffer, msgpack doesn't
+				* understand WordArrays */
+				data = BufferUtils.toArrayBuffer(data);
+			}
 		}
 		result.data = data;
 		return result;
diff --git a/nodejs/lib/util/bufferutils.js b/nodejs/lib/util/bufferutils.js
index 2ff26a1ad5..df76b1291e 100644
--- a/nodejs/lib/util/bufferutils.js
+++ b/nodejs/lib/util/bufferutils.js
@@ -7,6 +7,8 @@ this.BufferUtils = (function() {
 
 	BufferUtils.isBuffer = Buffer.isBuffer;
 
+	BufferUtils.toArrayBuffer = function(buf) { return buf; };
+
 	BufferUtils.base64Encode = function(buf) { return buf.toString('base64'); };
 
 	BufferUtils.base64Decode = function(string) { return new Buffer(string, 'base64'); };