diff --git a/lib/jsonapi/renderer/cached_resources_processor.rb b/lib/jsonapi/renderer/cached_resources_processor.rb
index 080ee99..de42cb9 100644
--- a/lib/jsonapi/renderer/cached_resources_processor.rb
+++ b/lib/jsonapi/renderer/cached_resources_processor.rb
@@ -17,7 +17,7 @@ def initialize(cache)
       def process_resources
         [@primary, @included].each do |resources|
           cache_hash = cache_key_map(resources)
-          processed_resources = @cache.fetch_multi(cache_hash.keys) do |key|
+          processed_resources = @cache.fetch_multi(*cache_hash.keys) do |key|
             res, include, fields = cache_hash[key]
             json = res.as_jsonapi(include: include, fields: fields).to_json
 
diff --git a/spec/caching_spec.rb b/spec/caching_spec.rb
index f153ba7..35c605c 100644
--- a/spec/caching_spec.rb
+++ b/spec/caching_spec.rb
@@ -5,7 +5,7 @@ def initialize
     @cache = {}
   end
 
-  def fetch_multi(keys)
+  def fetch_multi(*keys)
     keys.each_with_object({}) do |k, h|
       @cache[k] = yield(k) unless @cache.key?(k)
       h[k] = @cache[k]