diff --git a/lib/http/cookie_jar/mozilla_store.rb b/lib/http/cookie_jar/mozilla_store.rb
index ffc02ec..7b6e325 100644
--- a/lib/http/cookie_jar/mozilla_store.rb
+++ b/lib/http/cookie_jar/mozilla_store.rb
@@ -73,7 +73,7 @@ class HTTP::CookieJar
     # Closes the SQLite3 database.  After closing, any operation may
     # raise an error.
     def close
-      @db.close
+      @db.closed? || @db.close
       self
     end