diff --git a/lib/cached_resource/caching.rb b/lib/cached_resource/caching.rb
index b7ccacf..648e7a4 100644
--- a/lib/cached_resource/caching.rb
+++ b/lib/cached_resource/caching.rb
@@ -150,7 +150,7 @@ def _cache_write(key, object, *arguments)
       # Clear the cache.
       def cache_clear(options = nil)
         # Memcache doesn't support delete_matched, which can also be computationally expensive
-        if (Object.const_defined?(:Dalli) && cached_resource.cache.class.instance_of?("ActiveSupport::Cache::MemCacheStore")) || options.try(:fetch, :all)
+        if (Object.const_defined?(:Dalli) && cached_resource.cache.instance_of?(ActiveSupport::Cache::MemCacheStore)) || options.try(:fetch, :all)
           cached_resource.cache.clear.tap do |result|
             cached_resource.logger.info("#{CachedResource::Configuration::LOGGER_PREFIX} CLEAR ALL")
           end
@@ -162,8 +162,8 @@ def cache_clear(options = nil)
       end
 
       def cache_key_delete_pattern
-        case cached_resource.cache.class.to_s
-        when "ActiveSupport::Cache::MemoryStore", "ActiveSupport::Cache::FileStore"
+        case cached_resource.cache
+        when ActiveSupport::Cache::MemoryStore, ActiveSupport::Cache::FileStore
           /^#{name_key}\//
         else
           "#{name_key}/*"
diff --git a/spec/cached_resource/caching_spec.rb b/spec/cached_resource/caching_spec.rb
index 54d74c2..b0d58bf 100644
--- a/spec/cached_resource/caching_spec.rb
+++ b/spec/cached_resource/caching_spec.rb
@@ -321,19 +321,26 @@ def read_from_cache(key, model = Thing)
   end
 
   describe "#cache_key_delete_pattern" do
-    let(:cache_class_name) { "Redis" }
+    let(:cache_class) { "Redis" }
+
     before do
-      allow(Thing.cached_resource).to receive(:cache).and_return(double(class: cache_class_name))
+      allow(Thing.cached_resource).to receive(:cache).and_return(cache_class)
     end
 
-    ["ActiveSupport::Cache::MemoryStore", "ActiveSupport::Cache::FileStore"].each do |cache_name|
-      context "with cache #{cache_name}" do
-        let(:cache_class_name) { cache_name }
-        it do
-          expect(Thing.send(:cache_key_delete_pattern)).to eq(/^thing\//)
-        end
+    context "with cache ActiveSupport::Cache::MemoryStore" do
+      let(:cache_class) { ActiveSupport::Cache::MemoryStore.new }
+      it do
+        expect(Thing.send(:cache_key_delete_pattern)).to eq(/^thing\//)
+      end
+    end
+
+    context "with cache ActiveSupport::Cache::FileStore" do
+      let(:cache_class) { ActiveSupport::Cache::FileStore.new('tmp/') }
+      it do
+        expect(Thing.send(:cache_key_delete_pattern)).to eq(/^thing\//)
       end
     end
+
     context "default" do
       it do
         expect(Thing.send(:cache_key_delete_pattern)).to eq("thing/*")