diff --git a/lib/image_optim/cache.rb b/lib/image_optim/cache.rb
index 4e062e57..7387311a 100644
--- a/lib/image_optim/cache.rb
+++ b/lib/image_optim/cache.rb
@@ -34,6 +34,7 @@ def fetch(original)
       if optimized
         tmp = FSPath.temp_file_path(digest, @cache_dir)
         FileUtils.mv(optimized, tmp)
+        tmp.chmod(0o666 & ~File.umask)
         tmp.rename(cached)
         cached_path = CachePath.convert(cached)
 
diff --git a/spec/image_optim/cache_spec.rb b/spec/image_optim/cache_spec.rb
index 07b5ab4f..0167e1f8 100644
--- a/spec/image_optim/cache_spec.rb
+++ b/spec/image_optim/cache_spec.rb
@@ -72,6 +72,9 @@
           expect(FileUtils).to receive(:mv).with(optimized, tmp_file)
           expect(tmp_file).to receive(:rename).with(cached)
 
+          allow(File).to receive(:umask).and_return(0o024)
+          expect(tmp_file).to receive(:chmod).with(0o642)
+
           expect(cache.fetch(original){ optimized }).to eq(cached)
         end