diff --git a/lib/prome/rails.rb b/lib/prome/rails.rb
index fec72b1..778acce 100644
--- a/lib/prome/rails.rb
+++ b/lib/prome/rails.rb
@@ -16,10 +16,10 @@ def self.install!
         duration = ending - start
 
         Prome.get(:rails_requests_total).increment(labels)
-        Prome.get(:rails_request_duration_seconds).observe(labels, ms2s(duration))
+        Prome.get(:rails_request_duration_seconds).observe(labels, duration)
         Prome.get(:rails_view_runtime_seconds).observe(labels, ms2s(payload[:view_runtime]))
         Prome.get(:rails_db_runtime_seconds).observe(labels, ms2s(payload[:db_runtime]))
       end
     end
   end
-end
\ No newline at end of file
+end