diff --git a/toolkit/mozapps/extensions/internal/XPIProvider.jsm b/toolkit/mozapps/extensions/internal/XPIProvider.jsm
index fe21b98b2926..649fb4cfb866 100644
--- a/toolkit/mozapps/extensions/internal/XPIProvider.jsm
+++ b/toolkit/mozapps/extensions/internal/XPIProvider.jsm
@@ -86,6 +86,8 @@ XPCOMUtils.defineLazyGetter(this, "CertUtils", function() {
   return certUtils;
 });
 
+Cu.importGlobalProperties(["URL"]);
+
 const nsIFile = Components.Constructor("@mozilla.org/file/local;1", "nsIFile",
                                        "initWithPath");
 
@@ -7247,7 +7249,12 @@ AddonWrapper.prototype = {
     let addon = addonFor(this);
     if (addon.optionsURL) {
       if (this.isWebExtension) {
-        return ExtensionManagement.getURLForExtension(addon.id, addon.optionsURL);
+        // The internal object's optionsURL property comes from the addons
+        // DB and should be a relative URL.  However, extensions with
+        // options pages installed before bug 1293721 was fixed got absolute
+        // URLs in the addons db.  This code handles both cases.
+        let base = ExtensionManagement.getURLForExtension(addon.id);
+        return new URL(addon.optionsURL, base).href;
       }
       return addon.optionsURL;
     }