--- a/toolkit/components/extensions/ExtensionTestCommon.jsm
+++ b/toolkit/components/extensions/ExtensionTestCommon.jsm
@@ -215,26 +215,34 @@ this.ExtensionTestCommon = class Extensi
           <RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
                xmlns:em="http://www.mozilla.org/2004/em-rdf#">
               <Description about="urn:mozilla:install-manifest"
                   em:id="${manifest.applications.gecko.id}"
                   em:name="${manifest.name}"
                   em:type="2"
                   em:version="${manifest.version}"
                   em:description=""
+                  em:multiprocessCompatible="true"
                   em:hasEmbeddedWebExtension="true"
                   em:bootstrap="true">
 
                   <!-- Firefox -->
                   <em:targetApplication>
                       <Description
                           em:id="{ec8030f7-c20a-464f-9b0e-13a3a9e97384}"
                           em:minVersion="51.0a1"
                           em:maxVersion="*"/>
                   </em:targetApplication>
+                  <em:targetApplication>
+                    <Description>
+                      <em:id>toolkit@mozilla.org</em:id>
+                      <em:minVersion>0</em:minVersion>
+                      <em:maxVersion>*</em:maxVersion>
+                    </Description>
+                  </em:targetApplication>
               </Description>
           </RDF>
         `,
 
         "bootstrap.js": `
           function install() {}
           function uninstall() {}
           function shutdown() {}