diff --git a/lib/http/cookie_jar/abstract_store.rb b/lib/http/cookie_jar/abstract_store.rb
index 35d0b94..9c062ed 100644
--- a/lib/http/cookie_jar/abstract_store.rb
+++ b/lib/http/cookie_jar/abstract_store.rb
@@ -17,8 +17,8 @@ class HTTP::CookieJar::AbstractStore
       begin
         require 'http/cookie_jar/%s_store' % symbol
         @@class_map.fetch(symbol)
-      rescue LoadError, IndexError
-        raise IndexError, 'cookie store unavailable: %s' % symbol.inspect
+      rescue LoadError, IndexError => e
+        raise IndexError, 'cookie store unavailable: %s, error: %s' % symbol.inspect, e.message
       end
     end