diff --git a/lib/html/pipeline/camo_filter.rb b/lib/html/pipeline/camo_filter.rb
index 8441072e..b63f4738 100644
--- a/lib/html/pipeline/camo_filter.rb
+++ b/lib/html/pipeline/camo_filter.rb
@@ -56,8 +56,7 @@ def asset_proxy_url(url)
 
       # Private: calculate the HMAC digest for a image source URL.
       def asset_url_hash(url)
-        digest = OpenSSL::Digest::Digest.new('sha1')
-        OpenSSL::HMAC.hexdigest(digest, asset_proxy_secret_key, url)
+        OpenSSL::HMAC.hexdigest('sha1', asset_proxy_secret_key, url)
       end
 
       # Private: Return true if asset proxy filter should be enabled