diff --git a/js/libtextsecure.js b/js/libtextsecure.js
index 97c3785ee..ff4c8d7e1 100644
--- a/js/libtextsecure.js
+++ b/js/libtextsecure.js
@@ -40116,19 +40116,21 @@ window.textsecure.messaging = function() {
  * vim: ts=4:sw=4:expandtab
  */
 function ContactBuffer(arrayBuffer) {
-    this.buffer = new dCodeIO.ByteBuffer(arrayBuffer);
+    this.buffer = new dcodeIO.ByteBuffer();
+    this.buffer.append(arrayBuffer);
+    this.buffer.offset = 0;
+    this.buffer.limit = arrayBuffer.byteLength;
 }
 ContactBuffer.prototype = {
     constructor: ContactBuffer,
     readContact: function() {
         try {
             var len = this.buffer.readVarint32();
+            var contactInfoBuffer = this.buffer.slice(this.buffer.offset, this.buffer.offset+len);
+            var contactInfo = textsecure.protobuf.ContactDetails.decode(contactInfoBuffer);
             this.buffer.skip(len);
-            var contactInfo = textsecure.protobuf.ContactDetails.decode(
-                this.buffer.slice(this.buffer.offset, len)
-            );
-            var attachmentLen = contactInfo.avatar.length;
-            contactInfo.avatar.data = this.buffer.slice(this.buffer.offset, attachmentLen).toArrayBuffer(true /* copy? */);
+            var attachmentLen = contactInfo.avatar.length.toNumber();
+            contactInfo.avatar.data = this.buffer.slice(this.buffer.offset, this.buffer.offset + attachmentLen).toArrayBuffer(true);
             this.buffer.skip(attachmentLen);
 
             return contactInfo;
diff --git a/libtextsecure/contacts_parser.js b/libtextsecure/contacts_parser.js
index 9790e4589..4c954d391 100644
--- a/libtextsecure/contacts_parser.js
+++ b/libtextsecure/contacts_parser.js
@@ -2,19 +2,21 @@
  * vim: ts=4:sw=4:expandtab
  */
 function ContactBuffer(arrayBuffer) {
-    this.buffer = new dCodeIO.ByteBuffer(arrayBuffer);
+    this.buffer = new dcodeIO.ByteBuffer();
+    this.buffer.append(arrayBuffer);
+    this.buffer.offset = 0;
+    this.buffer.limit = arrayBuffer.byteLength;
 }
 ContactBuffer.prototype = {
     constructor: ContactBuffer,
     readContact: function() {
         try {
             var len = this.buffer.readVarint32();
+            var contactInfoBuffer = this.buffer.slice(this.buffer.offset, this.buffer.offset+len);
+            var contactInfo = textsecure.protobuf.ContactDetails.decode(contactInfoBuffer);
             this.buffer.skip(len);
-            var contactInfo = textsecure.protobuf.ContactDetails.decode(
-                this.buffer.slice(this.buffer.offset, len)
-            );
-            var attachmentLen = contactInfo.avatar.length;
-            contactInfo.avatar.data = this.buffer.slice(this.buffer.offset, attachmentLen).toArrayBuffer(true /* copy? */);
+            var attachmentLen = contactInfo.avatar.length.toNumber();
+            contactInfo.avatar.data = this.buffer.slice(this.buffer.offset, this.buffer.offset + attachmentLen).toArrayBuffer(true);
             this.buffer.skip(attachmentLen);
 
             return contactInfo;
diff --git a/libtextsecure/test/contacts_parser_test.js b/libtextsecure/test/contacts_parser_test.js
new file mode 100644
index 000000000..57de48350
--- /dev/null
+++ b/libtextsecure/test/contacts_parser_test.js
@@ -0,0 +1,61 @@
+/* vim: ts=4:sw=4
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+'use strict';
+
+describe("ContactsBuffer", function() {
+  function getTestBuffer() {
+    var buffer = new dcodeIO.ByteBuffer();
+    var avatarBuffer = new dcodeIO.ByteBuffer();
+    var avatarLen = 255;
+    for (var i=0; i < avatarLen; ++i) {
+      avatarBuffer.writeUint8(i);
+    }
+    avatarBuffer.limit = avatarBuffer.offset;
+    avatarBuffer.offset = 0;
+    var contactInfo = new textsecure.protobuf.ContactDetails({
+      name: "Zero Cool",
+      number: "+10000000000",
+      avatar: { contentType: "image/jpg", length: avatarLen }
+    });
+    var contactInfoBuffer = contactInfo.encode().toArrayBuffer();
+
+    for (var i = 0; i < 3; ++i) {
+      buffer.writeVarint32(contactInfoBuffer.byteLength);
+      buffer.append(contactInfoBuffer);
+      buffer.append(avatarBuffer.clone());
+    }
+
+    buffer.offset = 0;
+    buffer.limit = buffer.buffer.byteLength;
+    return buffer.toArrayBuffer();
+  }
+
+  it("parses an array buffer of contacts", function() {
+    var arrayBuffer = getTestBuffer();
+    var contactBuffer = new ContactBuffer(arrayBuffer);
+    for (var i=0; i < 3; ++i) {
+      var contact = contactBuffer.readContact();
+      assert.strictEqual(contact.name, "Zero Cool");
+      assert.strictEqual(contact.number, "+10000000000");
+      assert.strictEqual(contact.avatar.contentType, "image/jpg");
+      var avatarBytes = new Uint8Array(contact.avatar.data);
+      for (var j=0; j < 255; ++j) {
+        assert.strictEqual(avatarBytes[j],j);
+      }
+    }
+  });
+});
diff --git a/libtextsecure/test/index.html b/libtextsecure/test/index.html
index e740fdae4..312d959bb 100644
--- a/libtextsecure/test/index.html
+++ b/libtextsecure/test/index.html
@@ -46,11 +46,13 @@
   <script type="text/javascript" src="../api.js"></script>
   <script type="text/javascript" src="../sendmessage.js" data-cover></script>
   <script type="text/javascript" src="../account_manager.js" data-></script>
+  <script type="text/javascript" src="../contacts_parser.js"></script>
 
   <script type="text/javascript" src="fake_api.js"></script>
   <script type="text/javascript" src="helpers_test.js"></script>
   <script type="text/javascript" src="websocket-resources_test.js"></script>
   <script type="text/javascript" src="storage_test.js"></script>
+  <script type="text/javascript" src="contacts_parser_test.js"></script>
   <script type="text/javascript" src="generate_keys_test.js"></script>
   <script type="text/javascript" src="websocket_test.js"></script>
 </body>