diff --git a/chrome/content/zotero/preferences/preferences_export.js b/chrome/content/zotero/preferences/preferences_export.js
index 41c94a5c5..1f134e88d 100644
--- a/chrome/content/zotero/preferences/preferences_export.js
+++ b/chrome/content/zotero/preferences/preferences_export.js
@@ -177,7 +177,8 @@ Zotero_Preferences.Export = {
 		}
 		
 		var io = {domain: domain, format: format, ok: false};
-		window.openDialog('chrome://zotero/content/preferences/quickCopySiteEditor.xul', "zotero-preferences-quickCopySiteEditor", "chrome, modal", io);
+		window.openDialog('chrome://zotero/content/preferences/quickCopySiteEditor.xul',
+			"zotero-preferences-quickCopySiteEditor", "chrome,modal,centerscreen", io);
 		
 		if (!io.ok) {
 			return;
diff --git a/chrome/content/zotero/preferences/preferences_proxies.js b/chrome/content/zotero/preferences/preferences_proxies.js
index fd7a4751e..c4e0f4db3 100644
--- a/chrome/content/zotero/preferences/preferences_proxies.js
+++ b/chrome/content/zotero/preferences/preferences_proxies.js
@@ -72,7 +72,8 @@ Zotero_Preferences.Proxies = {
 	showProxyEditor: function (index) {
 		if(index == -1) return;
 		window.openDialog('chrome://zotero/content/preferences/proxyEditor.xul',
-			"zotero-preferences-proxyEditor", "chrome, modal", index !== undefined ? this._proxies[index] : null);
+			"zotero-preferences-proxyEditor", "chrome,modal,centerscreen",
+			index !== undefined ? this._proxies[index] : null);
 		this.refreshProxyList();
 	},