--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -5020,17 +5020,18 @@ nsBrowserAccess.prototype = {
 
     var isExternal = !!(aFlags & Ci.nsIBrowserDOMWindow.OPEN_EXTERNAL);
 
     var userContextId = aParams.openerOriginAttributes &&
                         ("userContextId" in aParams.openerOriginAttributes)
                           ? aParams.openerOriginAttributes.userContextId
                           : Ci.nsIScriptSecurityManager.DEFAULT_USER_CONTEXT_ID
 
-    let browser = this._openURIInNewTab(aURI, aParams.referrer,
+    let referrer = aParams.referrer ? makeURI(aParams.referrer) : null;
+    let browser = this._openURIInNewTab(aURI, referrer,
                                         aParams.referrerPolicy,
                                         aParams.isPrivate,
                                         isExternal, false,
                                         userContextId);
     if (browser)
       return browser.QueryInterface(Ci.nsIFrameLoaderOwner);
 
     return null;