--- a/toolkit/mozapps/extensions/internal/XPIProvider.jsm
+++ b/toolkit/mozapps/extensions/internal/XPIProvider.jsm
@@ -7965,16 +7965,22 @@ Object.assign(SystemAddonInstallLocation
   },
 
   /**
    * Removes any directories not currently in use or pending use after a
    * restart. Any errors that happen here don't really matter as we'll attempt
    * to cleanup again next time.
    */
   cleanDirectories: Task.async(function*() {
+
+    // System add-ons directory does not exist
+    if (!(yield OS.File.exists(this._baseDir.path))) {
+      return;
+    }
+
     let iterator;
     try {
       iterator = new OS.File.DirectoryIterator(this._baseDir.path);
     }
     catch (e) {
       logger.error("Failed to clean updated system add-ons directories.", e);
       return;
     }