diff --git a/lib/rack/attack/store_proxy.rb b/lib/rack/attack/store_proxy.rb
index c88fb6b..d88ad67 100644
--- a/lib/rack/attack/store_proxy.rb
+++ b/lib/rack/attack/store_proxy.rb
@@ -2,30 +2,25 @@ module Rack
   class Attack
     module StoreProxy
       PROXIES = [DalliProxy, MemCacheProxy, RedisStoreProxy]
-      USE_BASE_CLIENT = ['Redis::Store', 'Dalli::Client', 'MemCache']
 
       def self.build(store)
         # RedisStore#increment needs different behavior, so detect that
         # (method has an arity of 2; must call #expire separately
-        client = fetch_client(store)
-        klass = PROXIES.find { |proxy| proxy.handle?(client) }
-        klass ? klass.new(client) : client
-      end
+        if (defined?(::ActiveSupport::Cache::RedisStore) && store.is_a?(::ActiveSupport::Cache::RedisStore)) ||
+          (defined?(::ActiveSupport::Cache::MemCacheStore) && store.is_a?(::ActiveSupport::Cache::MemCacheStore))
 
-      def self.fetch_client(store)
-        client = store.instance_variable_get(:@data)
-        # RedisStore#increment needs different behavior, so detect that
-        # (method has an arity of 2; must call #expire separately
-        #
-        # ActiveSupport::Cache::RedisStore doesn't expose any way to set an expiry,
-        # so use the raw Redis::Store instead.
-        #
-        # We also want to use the underlying Dalli client instead of ::ActiveSupport::Cache::MemCacheStore,
-        # and the MemCache client if using Rails 3.x
-        USE_BASE_CLIENT.each do |klass|
-          return client if !client.nil? && Object.const_defined?(klass) && client.is_a?(Object.const_get(klass))
+          # ActiveSupport::Cache::RedisStore doesn't expose any way to set an expiry,
+          # so use the raw Redis::Store instead.
+          # We also want to use the underlying Dalli client instead of ::ActiveSupport::Cache::MemCacheStore,
+          # and the MemCache client if using Rails 3.x
+          client = store.instance_variable_get(:@data)
+          if (defined?(::Redis::Store) && client.is_a?(Redis::Store)) ||
+            (defined?(Dalli::Client) && client.is_a?(Dalli::Client)) || (defined?(MemCache) && client.is_a?(MemCache))
+            store = store.instance_variable_get(:@data)
+          end
         end
-        return store
+        klass = PROXIES.find { |proxy| proxy.handle?(store) }
+        klass ? klass.new(store) : store
       end
 
     end