diff --git a/chrome/content/zotero/hardConfirmationDialog.js b/chrome/content/zotero/hardConfirmationDialog.js
index 44809c77b6..758e0c85c3 100644
--- a/chrome/content/zotero/hardConfirmationDialog.js
+++ b/chrome/content/zotero/hardConfirmationDialog.js
@@ -25,10 +25,14 @@
 
 Zotero.HardConfirmationDialog = {
 	init: function() {
+		document.addEventListener('dialogaccept', () => Zotero.HardConfirmationDialog.onAccept());
+		document.addEventListener('dialogextra1', () => Zotero.HardConfirmationDialog.onExtra1());
+		document.addEventListener('dialogextra2', () => Zotero.HardConfirmationDialog.onExtra2());
+
 		this.io = window.arguments[0];
 		
-		Zotero.setFontSize(document.getElementById('zotero-hardConfirmationDialog'));
-		
+		Zotero.setFontSize(document.documentElement);
+		var dialog = document.getElementById('commonDialog');
 		var vbox = document.getElementById('infoContainer');
 		var sep = vbox.firstChild;
 		
@@ -56,25 +60,25 @@ Zotero.HardConfirmationDialog = {
 		}
 		
 		if (this.io.acceptLabel) {
-			document.documentElement.getButton('accept').label = this.io.acceptLabel
+			dialog.getButton('accept').label = this.io.acceptLabel
 		}
 		if (this.io.extra1Label) {
-			document.documentElement.buttons = document.documentElement.buttons + ',extra1';
-			document.documentElement.getButton('extra1').label = this.io.extra1Label
+			dialog.buttons = dialog.buttons + ',extra1';
+			dialog.getButton('extra1').label = this.io.extra1Label
 		}
 		if (this.io.extra2Label) {
-			document.documentElement.buttons = document.documentElement.buttons + ',extra2';
-			document.documentElement.getButton('extra2').label = this.io.extra2Label
+			dialog.buttons = dialog.buttons + ',extra2';
+			dialog.getButton('extra2').label = this.io.extra2Label
 		}
 	},
 	
 	onCheckbox: function(event) {
-		document.documentElement.getButton('accept').disabled = 
+		document.getElementById('commonDialog').getButton('accept').disabled = 
 			!document.getElementById('zotero-hardConfirmationDialog-checkbox').checked;
 	},
 	
 	onKeyUp: function(event) {
-		document.documentElement.getButton('accept').disabled = 
+		document.getElementById('commonDialog').getButton('accept').disabled = 
 			document.getElementById('zotero-hardConfirmationDialog-textbox').value != this.io.confirmationText;
 	},
 	
@@ -84,11 +88,11 @@ Zotero.HardConfirmationDialog = {
 	
 	onExtra1: function() {
 		this.io.extra1 = true;
-		document.documentElement.cancelDialog();
+		document.getElementById('commonDialog').cancelDialog();
 	},
 	
 	onExtra2: function() {
 		this.io.extra2 = true;
-		document.documentElement.cancelDialog();
+		document.getElementById('commonDialog').cancelDialog();
 	}
 };
diff --git a/chrome/content/zotero/hardConfirmationDialog.xul b/chrome/content/zotero/hardConfirmationDialog.xhtml
similarity index 59%
rename from chrome/content/zotero/hardConfirmationDialog.xul
rename to chrome/content/zotero/hardConfirmationDialog.xhtml
index 771f1e64a6..4490e11c38 100644
--- a/chrome/content/zotero/hardConfirmationDialog.xul
+++ b/chrome/content/zotero/hardConfirmationDialog.xhtml
@@ -32,36 +32,29 @@
 
 <!DOCTYPE overlay [ <!ENTITY % zoteroDTD SYSTEM "chrome://zotero/locale/zotero.dtd"> %zoteroDTD; ]>
 
-<dialog xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
-	title="" buttons="cancel,accept"
-	id="zotero-hardConfirmationDialog"
-	onload="Zotero.HardConfirmationDialog.init(); sizeToContent();"
-	ondialogaccept="Zotero.HardConfirmationDialog.onAccept();"
-	ondialogextra1="Zotero.HardConfirmationDialog.onExtra1();"
-	ondialogextra2="Zotero.HardConfirmationDialog.onExtra2();">
+<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+		xmlns:html="http://www.w3.org/1999/xhtml"
+		title=""
+		onload="Zotero.HardConfirmationDialog.init(); sizeToContent();"
+		style="display: flex;">
+<dialog 
+	buttons="cancel,accept"
+	id="commonDialog">
 	
 	<script src="chrome://zotero/content/include.js"/>
 	<script src="hardConfirmationDialog.js"/>
 	
-	<grid>
-		<columns>
-			<column/>
-			<column flex="1"/>
-		</columns>
-		<rows>
-			<row>
-				<hbox id="iconContainer" align="start"><image id="info.icon" class="spaced alert-icon"/></hbox>
-				<vbox id="infoContainer">
-					<description id="infoTitle" hidden="true"/>
-					<description id="infoBody"/>
-					
-					<separator class="thin"/>
+	<hbox>
+		<hbox id="iconContainer" align="start"><image id="info.icon" class="spaced alert-icon"/></hbox>
+		<vbox id="infoContainer" flex="1">
+			<description id="infoTitle" hidden="true"/>
+			<description id="infoBody"/>
+			
+			<separator class="thin"/>
 
-					<checkbox id="zotero-hardConfirmationDialog-checkbox" hidden="true" oncommand="Zotero.HardConfirmationDialog.onCheckbox(event)"/>
-					<textbox id="zotero-hardConfirmationDialog-textbox" hidden="true" onkeyup="Zotero.HardConfirmationDialog.onKeyUp(event)"/>
-				</vbox>
-			</row>
-		</rows>
-	</grid>
-	
+			<checkbox id="zotero-hardConfirmationDialog-checkbox" hidden="true" oncommand="Zotero.HardConfirmationDialog.onCheckbox(event)"/>
+			<html:input id="zotero-hardConfirmationDialog-textbox" type="text" hidden="true" onkeyup="Zotero.HardConfirmationDialog.onKeyUp(event)"/>
+		</vbox>
+	</hbox>
 </dialog>
+</window>
\ No newline at end of file
diff --git a/chrome/content/zotero/xpcom/sync/syncLocal.js b/chrome/content/zotero/xpcom/sync/syncLocal.js
index 9590732a56..ce5dac9769 100644
--- a/chrome/content/zotero/xpcom/sync/syncLocal.js
+++ b/chrome/content/zotero/xpcom/sync/syncLocal.js
@@ -140,7 +140,7 @@ Zotero.Sync.Data.Local = {
 				acceptLabel: Zotero.getString('account.confirmDelete.button'),
 				extra2Label: Zotero.getString('general.moreInformation')
 			};
-			win.openDialog("chrome://zotero/content/hardConfirmationDialog.xul", "",
+			win.openDialog("chrome://zotero/content/hardConfirmationDialog.xhtml", "",
 				"chrome,dialog,modal,centerscreen", io);
 			
 			if (io.accept) {
diff --git a/test/tests/syncLocalTest.js b/test/tests/syncLocalTest.js
index 19b25da955..12c395183a 100644
--- a/test/tests/syncLocalTest.js
+++ b/test/tests/syncLocalTest.js
@@ -57,7 +57,7 @@ describe("Zotero.Sync.Data.Local", function() {
 					.dispatchEvent(new Event('command'));
 				
 				handled = true;
-			}, 'accept', 'chrome://zotero/content/hardConfirmationDialog.xul');
+			}, 'accept', 'chrome://zotero/content/hardConfirmationDialog.xhtml');
 			var cont = yield Zotero.Sync.Data.Local.checkUser(window, 2, "B");
 			var resetDataDirFileExists = yield OS.File.exists(resetDataDirFile);
 			assert.isTrue(handled);
@@ -69,7 +69,7 @@ describe("Zotero.Sync.Data.Local", function() {
 			yield Zotero.Users.setCurrentUserID(1);
 			yield Zotero.Users.setCurrentUsername("A");
 			
-			waitForDialog(false, 'cancel', 'chrome://zotero/content/hardConfirmationDialog.xul');
+			waitForDialog(false, 'cancel', 'chrome://zotero/content/hardConfirmationDialog.xhtml');
 			var cont = yield Zotero.Sync.Data.Local.checkUser(window, 2, "B");
 			var resetDataDirFileExists = yield OS.File.exists(resetDataDirFile);
 			assert.isFalse(cont);
@@ -85,7 +85,7 @@ describe("Zotero.Sync.Data.Local", function() {
 			yield Zotero.Users.setCurrentUserID(1);
 			yield Zotero.Users.setCurrentUsername("A");
 			
-			waitForDialog(null, 'extra1', 'chrome://zotero/content/hardConfirmationDialog.xul');
+			waitForDialog(null, 'extra1', 'chrome://zotero/content/hardConfirmationDialog.xhtml');
 			waitForDialog();
 			var cont = yield Zotero.Sync.Data.Local.checkUser(window, 2, "B");
 			var resetDataDirFileExists = yield OS.File.exists(resetDataDirFile);
@@ -110,7 +110,7 @@ describe("Zotero.Sync.Data.Local", function() {
 				item2.toJSON().relations[pred][0].startsWith('http://zotero.org/users/local/')
 			);
 			
-			waitForDialog(false, 'accept', 'chrome://zotero/content/hardConfirmationDialog.xul');
+			waitForDialog(false, 'accept', 'chrome://zotero/content/hardConfirmationDialog.xhtml');
 			yield Zotero.Sync.Data.Local.checkUser(window, 1, "A");
 			
 			assert.isTrue(