diff --git a/chrome/content/zotero/xpcom/zotero.js b/chrome/content/zotero/xpcom/zotero.js
index c8cd887c9..7de9fa749 100644
--- a/chrome/content/zotero/xpcom/zotero.js
+++ b/chrome/content/zotero/xpcom/zotero.js
@@ -35,7 +35,7 @@ const ZOTERO_CONFIG = {
 	API_URL: 'https://api.zotero.org/',
 	PREF_BRANCH: 'extensions.zotero.',
 	BOOKMARKLET_URL: 'https://www.zotero.org/bookmarklet/',
-	VERSION: "3.1a1.SOURCE"
+	VERSION: "4.0a1.SOURCE"
 };
 
 // Commonly used imports accessible anywhere
diff --git a/install.rdf b/install.rdf
index 1fb4bbf15..75a125ab1 100644
--- a/install.rdf
+++ b/install.rdf
@@ -6,7 +6,7 @@
   
     <em:id>zotero@chnm.gmu.edu</em:id>
     <em:name>Zotero</em:name>
-    <em:version>3.1a1.SOURCE</em:version>
+    <em:version>4.0a1.SOURCE</em:version>
     <em:creator>Center for History and New Media<br/>George Mason University</em:creator>
     <em:contributor>Dan Cohen</em:contributor>
     <em:contributor>Sean Takats</em:contributor>
@@ -25,7 +25,7 @@
       <Description>
         <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
         <em:minVersion>17.0</em:minVersion>
-        <em:maxVersion>20.*</em:maxVersion>
+        <em:maxVersion>21.*</em:maxVersion>
       </Description>
     </em:targetApplication>
     
diff --git a/update.rdf b/update.rdf
index 0cdbb6abb..034943baa 100644
--- a/update.rdf
+++ b/update.rdf
@@ -7,12 +7,12 @@
     <RDF:Seq>
       <RDF:li>
         <RDF:Description>
-          <version>3.1a1.SOURCE</version>
+          <version>4.0a1.SOURCE</version>
           <targetApplication>
             <RDF:Description>
               <id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</id>
               <minVersion>17.0</minVersion>
-              <maxVersion>20.*</maxVersion>
+              <maxVersion>21.*</maxVersion>
               <updateLink>http://download.zotero.org/extension/zotero.xpi</updateLink>
               <updateHash>sha1:</updateHash>
             </RDF:Description>