diff --git a/chrome/content/zotero/preferences/preferences_firefox.xul b/chrome/content/zotero/preferences/preferences_firefox.xul
index 07dc62428a..bfb1e50e07 100644
--- a/chrome/content/zotero/preferences/preferences_firefox.xul
+++ b/chrome/content/zotero/preferences/preferences_firefox.xul
@@ -23,7 +23,10 @@
     
     ***** END LICENSE BLOCK *****
 -->
-<!DOCTYPE prefwindow SYSTEM "chrome://zotero/locale/preferences.dtd">
+<!DOCTYPE prefwindow [
+	<!ENTITY % preferencesDTD SYSTEM "chrome://zotero/locale/preferences.dtd"> %preferencesDTD;
+	<!ENTITY % zoteroDTD SYSTEM "chrome://zotero/locale/zotero.dtd"> %zoteroDTD;
+]>
 
 <?xml-stylesheet href="chrome://global/skin/global.css"?>
 <?xml-stylesheet href="chrome://browser/skin/preferences/preferences.css"?>
@@ -64,7 +67,7 @@
 				<caption label="&zotero.preferences.proxies.configured;"/>
 				
 				<tree id="proxyTree" hidecolumnpicker="true" rows="6" seltype="single"
-						ondblclick="Zotero_Preferences.Proxies.showProxyEditor(this.currentIndex)" onselect="document.getElementById('proxyTree-delete').disabled = undefined"
+						ondblclick="Zotero_Preferences.Proxies.showProxyEditor(this.currentIndex)" onselect="Zotero_Preferences.Proxies.enableProxyButtons()"
 						onkeypress="if (event.keyCode == event.DOM_VK_DELETE) { Zotero_Preferences.Proxies.deleteProxy(); }">
 					<treecols>
 						<treecol id="proxyTree-hostname" label="&zotero.preferences.proxies.hostname;" flex="1"/>
@@ -73,7 +76,9 @@
 					<treechildren id="proxyTree-rows"/>
 				</tree>
 				<separator class="thin"/>
-				<hbox pack="end">
+				<hbox>
+					<button disabled="true" id="proxyTree-edit" label="&zotero.general.edit;" onclick="Zotero_Preferences.Proxies.showProxyEditor(document.getElementById('proxyTree').currentIndex)"/>
+					<spacer flex="1"/>
 					<button disabled="true" id="proxyTree-delete" label="-" onclick="Zotero_Preferences.Proxies.deleteProxy()"/>
 					<button label="+" id="proxyTree-add" onclick="Zotero_Preferences.Proxies.showProxyEditor()"/>
 				</hbox>
diff --git a/chrome/content/zotero/preferences/preferences_proxies.js b/chrome/content/zotero/preferences/preferences_proxies.js
index b0227396f6..6c081a18f5 100644
--- a/chrome/content/zotero/preferences/preferences_proxies.js
+++ b/chrome/content/zotero/preferences/preferences_proxies.js
@@ -55,6 +55,14 @@ Zotero_Preferences.Proxies = {
 	},
 	
 	
+	/**
+	 * Enables UI buttons when proxy is selected
+	 */
+	enableProxyButtons: function () {
+		document.getElementById('proxyTree-edit').disabled = false;
+		document.getElementById('proxyTree-delete').disabled = false;
+	},
+	
 	/**
 	 * Adds a proxy to the proxy pane
 	 */
@@ -138,6 +146,7 @@ Zotero_Preferences.Proxies = {
 		}
 		
 		document.getElementById('proxyTree').currentIndex = -1;
+		document.getElementById('proxyTree-edit').disabled = true;
 		document.getElementById('proxyTree-delete').disabled = true;
 		document.getElementById('zotero-proxies-transparent').checked = Zotero.Prefs.get("proxies.transparent");
 		document.getElementById('zotero-proxies-autoRecognize').checked = Zotero.Prefs.get("proxies.autoRecognize");