diff --git a/dist/barometer-test.js b/dist/barometer-test.js
index 259261f..656dd12 100644
--- a/dist/barometer-test.js
+++ b/dist/barometer-test.js
@@ -211,7 +211,7 @@ transport._flushBuffer = function (pageEnd) {
   if (navigator.sendBeacon) {
     navigator.sendBeacon(url, JSON.stringify(bufferToSend))
   } else {
-    var xhr = new xhrStats._XMLHttpRequest()
+    var xhr = new window.XMLHttpRequest()
     xhr.open('POST', url, !pageEnd)
     xhr.setRequestHeader('Content-Type', 'application/json')
     xhr.send(JSON.stringify(bufferToSend))
@@ -1498,7 +1498,7 @@ function drainQueue() {
     if (draining) {
         return;
     }
-    var timeout = cachedSetTimeout(cleanUpNextTick);
+    var timeout = cachedSetTimeout.call(null, cleanUpNextTick);
     draining = true;
 
     var len = queue.length;
@@ -1515,7 +1515,7 @@ function drainQueue() {
     }
     currentQueue = null;
     draining = false;
-    cachedClearTimeout(timeout);
+    cachedClearTimeout.call(null, timeout);
 }
 
 process.nextTick = function (fun) {
@@ -1527,7 +1527,7 @@ process.nextTick = function (fun) {
     }
     queue.push(new Item(fun, args));
     if (queue.length === 1 && !draining) {
-        cachedSetTimeout(drainQueue, 0);
+        cachedSetTimeout.call(null, drainQueue, 0);
     }
 };
 
@@ -2065,6 +2065,24 @@ var sinon = (function () { // eslint-disable-line no-unused-vars
             }
         }
 
+        function verifyIsValidAssertion(assertionMethod, assertionArgs) {
+            switch (assertionMethod) {
+                case "notCalled":
+                case "called":
+                case "calledOnce":
+                case "calledTwice":
+                case "calledThrice":
+                    if (assertionArgs.length !== 0) {
+                        assert.fail(assertionMethod +
+                                    " takes 1 argument but was called with " +
+                                    (assertionArgs.length + 1) + " arguments");
+                    }
+                    break;
+                default:
+                    break;
+            }
+        }
+
         function failAssertion(object, msg) {
             object = object || global;
             var failMethod = object.fail || assert.fail;
@@ -2081,6 +2099,8 @@ var sinon = (function () { // eslint-disable-line no-unused-vars
                 verifyIsStub(fake);
 
                 var args = slice.call(arguments, 1);
+                verifyIsValidAssertion(name, args);
+
                 var failed = false;
 
                 if (typeof method === "function") {
@@ -5464,7 +5484,7 @@ var sinon = (function () { // eslint-disable-line no-unused-vars
             }
 
             for (prop in a) {
-                if (a.hasOwnProperty(prop)) {
+                if (hasOwn.call(a, prop)) {
                     aLength += 1;
 
                     if (!(prop in b)) {
@@ -5478,7 +5498,7 @@ var sinon = (function () { // eslint-disable-line no-unused-vars
             }
 
             for (prop in b) {
-                if (b.hasOwnProperty(prop)) {
+                if (hasOwn.call(b, prop)) {
                     bLength += 1;
                 }
             }
@@ -6556,7 +6576,7 @@ if (typeof sinon === "undefined") {
         }
 
         var xhr = this;
-        var events = ["loadstart", "load", "abort", "loadend"];
+        var events = ["loadstart", "load", "abort", "error", "loadend"];
 
         function addEventListener(eventName) {
             xhr.addEventListener(eventName, function (event) {
@@ -6890,12 +6910,16 @@ if (typeof sinon === "undefined") {
                 }
 
                 if (this.readyState === FakeXMLHttpRequest.DONE) {
-                    if (this.status < 200 || this.status > 299) {
-                        progress = {loaded: 0, total: 0};
+                    // ensure loaded and total are numbers
+                    progress = {
+                      loaded: this.progress || 0,
+                      total: this.progress || 0
+                    };
+
+                    if (this.status === 0) {
                         event = this.aborted ? "abort" : "error";
                     }
                     else {
-                        progress = {loaded: 100, total: 100};
                         event = "load";
                     }
 
@@ -6988,6 +7012,15 @@ if (typeof sinon === "undefined") {
                 this.readyState = FakeXMLHttpRequest.UNSENT;
             },
 
+            error: function error() {
+                clearResponse(this);
+                this.errorFlag = true;
+                this.requestHeaders = {};
+                this.responseHeaders = {};
+
+                this.readyStateChange(FakeXMLHttpRequest.DONE);
+            },
+
             getResponseHeader: function getResponseHeader(header) {
                 if (this.readyState < FakeXMLHttpRequest.HEADERS_RECEIVED) {
                     return null;
@@ -7051,6 +7084,7 @@ if (typeof sinon === "undefined") {
                 } else if (this.responseType === "" && isXmlContentType(contentType)) {
                     this.responseXML = FakeXMLHttpRequest.parseXML(this.responseText);
                 }
+                this.progress = body.length;
                 this.readyStateChange(FakeXMLHttpRequest.DONE);
             },
 
diff --git a/dist/barometer.min.js b/dist/barometer.min.js
index 30d5972..6232222 100644
--- a/dist/barometer.min.js
+++ b/dist/barometer.min.js
@@ -1,2 +1,2 @@
 /*! barometer v1.0.0 */
-_='!
e t(na) a;r=a={œ:{id:n,„ed:!1}; e.call(r,r,r,tr.„ed=!0,r}a={}; t.m=%.c=a,t.p="Kt(0)}([
%,ae#1)=‚2Qa(6a(3a(7š‘,n	=r	,=r.3u#1Qš="XXXXXKe={’s:{ers:{}=0e(e8=8||0,8++Ke)n	%†=†||[],†.push(t)’K%)};o‘;toW<100W…oo=a,5e3)ae0›Wu.šoW(…oo‘Qt=;e(Qa=u.š;if(€)€(a,@Qelse{i=new r.n;i.op("POSTKa,!ei.RHeader("C`tt-TypeK"applicFi`/js`"i.sd(@i.timeout=4e3}}~n=ƒ;i=["UNSENTK"OPENEDK"HEADERS_RECEIVEDK"LOADINGK"DONE"];re"xhr."+eu%,an={“:a}rŽe)"_"›r[0]W0›e[r]W(n[r]=e[r]-tQ no,a,r=o(ši=u(Times,off,“)sŽi)t="timing$‡	(a,i[s]Qt="žs.(at="size	(a,(r.žText•.lgth)ƒe=new n;try{t={a=op,u=sd;opu,otry{s=;r(e,"readystFechangeK
t[i[]]=!1r(e,"„dK
a o({type:u,š:o,Times:t,off:s,“:-s,r:e})!1)}cFch(c} a,sd u}cFch(o} e,aZ?Z(t,a,!1):ˆWˆ("`"+t,a)a=(e•YŠ^https?:\\/\\//i,"")\\/*;(t•.mFch(/\\?/)W(a+=tYslice(1)\\/*a~u={a=™;e=toJSON()nŽe)"™"›nW0›eW(t=e-aQ tr=o(‰ref,‰ashQ"page„."+t”e*i%=.timing||{a=u(t)rŽa)e=r(ru	(e,a[r]Qo=(.i`||{}).—Count||0;e=r("—s"u	(e,o)"object"==typeof W("complete"===documt.?i():r(,"„Ki,!1)),r,u=e={o#4i#6s#2c=0;u.ss	(r,-n)u.fs.(–visits")nWu.s(c++;e=,t=c,a=0,o=[9,9,9,9,9],f=!1,g=25,l=–dynamic"p…dn=,r=–gagemt"Qt=125;s	(l,-e-t)d=
f=!06e3ve=;
n=,r=n-e-g;if(r>aW(a=r!ft›c) p(Qo.shift(o.push(r)u=0,i=0;i<5;i++)u+=o[i]; u<5Wa>25?p():void v,g)}g)};v()u.f(Œ?(o(,"popstF˜
e=‹;‹ u.f(t}}(Œ)):o(,"hashchang˜)}]Q
(
%,aknbuffervar .œreturnwindownew DFe	.’$r.stFu‡,t(++,‚.debugWc`sollog("Timeout(.apply(e,argumts)}){),count.Š[^a-z0-9-n.=e={r#readyStFe}
%ke%},equestnavigF.performancee.en;for(=
#=a($."+type”r”%e,t*]/gi,"_")8.ers[e]@JSON.stringify(t)FatK",Q);W&&Y.split("?")[0].ZaddEvtLister`onk"use strict";~}4u#2o#5Q[n]€or.sdBeac`Size‚.barometerƒ.XMLHttpR„load…clear†	s[e]‡s,a=r(tuˆFtachEvt‰.locFiohŠreplace(/‹pushStFeŒ.historysetŽ in if(et‘=null’gauge“total”+"."+•||"")–i.r("—redirect˜eKu.f,!1™i`Startšurl›!==œexportsfuncti`žresp`se';for(Y in $='žœ›š™˜—–•”“’‘ŽŒ‹Š‰ˆ‡†…„ƒ‚€~k`ZYWQKF@8*%$#	
')with(_.split($[Y]))_=join(pop());eval(_)
\ No newline at end of file
+_='!
e t(a™nŒ) nŒ;rYŒ={œ:{id:a,ƒed:!1}; eŒ.call(r,r,r,tr.ƒed=!0,r}n={}; t.m=e,t.cY,t.p="Zt(0)}([,neY(1)=‚WrY(2n(6n(3n(7šYull,a	=r	,=r.Wr=(n(3n(1)š="XXXXXZe$={s:{ers:{}=0e(Q8=8||0,8++Ze)a	=…=…||[],….push(t)Ze,t)};uYull;t$u`<100`„uu=n,5e3)nQ™0›`r.šu`(„uuYullt=;e(n=r.š;™€)€(n,@else{oYew #;o.op("POSTZn,!eo.RHeader("CFtt-TypeZ"applicKiF/jsF"o.sd(@o.timeout=4e3}}a=#;i=["UNSENTZ"OPENEDZ"HEADERS_RECEIVEDZ"LOADINGZ"DONE"];rQ"xhr."+eu=,na={:n}rŽe)"_"›r[0]`0›e[r]`(a[r]=e[r]-t aoQt,n,r=o(ši=u(Times,off,)sŽi)t="timing%†	(n,i[s]t="žs.(nt="size	(n,(r.žText’.lgth)#$eYew a;try{–op,u=sd;op=
u,otry{s=;r(e,"readystKechangeZ
t[i[]]=!1r(e,"ƒdZ
n o({type:u,š:o,Times:t,off:s,:-s,r:e})!1)}cKch(c} n,sd$ u}cKch(o} e˜,n~?~(t,n,!1):‡`‡("F"+t,n)˜n=(e’k‰^https?:\\/\\//i,"")\\/*;(t’.mKch(/\\?/)`(n+=tkslice(1)\\/*nuQ–—;e=toJSON()aŽe)"—"›a`0›eŒ`(tŒ=eŒ-n trQt=o(ˆref,ˆash"pageƒ."+t‘e*i$e,t=.timing||{n=u(t)rŽn)e=r(ru	(e,n[r]o=(.iF||{}).”Count||0;e=r("”s"u	(e,o)"object"==typeof `("complete"===documt.?i():r(,"ƒZi,!1)),r,uWoY(4iY(6sY(2c=0;u.s$s	(r,-a)u.f$s.(“visits")a`u.s(c++;e=,t=c,n=0,o=[9,9,9,9,9],f=!1,g=25,l=“dynamic"p$„da=,r=“gagemt"t=125;s	(l,-e-t)d=
f=!06e3v$e=;
a=,r=a-e-g;™r>n`(n=r!f™t›c) p(o.shift(o.push(r)u=0,i=0;i<5;i++)u+=o[i]; u<5`n>25?p():void v,g)}g)};v()u.f(‹?(o(,"popstK•
e™et=Š;Š$ u.f(t}}(‹)):o(,"hashchang•)}]
(,nabuffervar .œwindowreturnnew DKe	.%r.stKu†,t(++,‚.debug`cFsollog("Timeout(.apply(e,argumts)}){),count.‰[^a-z0-9-equest},a.readyStKe}WrY(4uY(2oY(5"use strict";navigK.performancee.
e,ten;for(#.XMLHttpR$=
%."+type‘r‘*]/gi,"_")8.ers[e]@JSON.stringify(t)FonKatQ=
eW=e={Y=nZ",`&&k.split("?")[0].~addEvtLister);€or.sdBeacFSize‚.barometerƒload„clear…	s[e]†s,n=r(tu‡KtachEvtˆ.locKiF.h‰replace(/ŠpushStKe‹.historyŒ[a]setŽ in gaugetotal‘+"."+’||"")“i.r("”redirect•eZu.f,!1–t={n=—iFStart˜}e=™if(šurl›!==œexportsfunctiFžrespFse';for(Y in $='žœ›š™˜—–•”“’‘ŽŒ‹Š‰ˆ‡†…„ƒ‚€~k`ZYWQKF@8*%$#	
')with(_.split($[Y]))_=join(pop());eval(_)
\ No newline at end of file
diff --git a/lib/transport.js b/lib/transport.js
index 6be38df..b572c54 100644
--- a/lib/transport.js
+++ b/lib/transport.js
@@ -57,7 +57,7 @@ transport._flushBuffer = function (pageEnd) {
   if (navigator.sendBeacon) {
     navigator.sendBeacon(url, JSON.stringify(bufferToSend))
   } else {
-    var xhr = new xhrStats._XMLHttpRequest()
+    var xhr = new window.XMLHttpRequest()
     xhr.open('POST', url, !pageEnd)
     xhr.setRequestHeader('Content-Type', 'application/json')
     xhr.send(JSON.stringify(bufferToSend))