diff --git a/addon/serverless.js b/addon/serverless.js
index ab85e61..2b9f4f1 100644
--- a/addon/serverless.js
+++ b/addon/serverless.js
@@ -46,7 +46,7 @@ router.get('/:configuration/:resource/:type/:id/:extra?.json', (req, res, next)
           staleError: 'stale-if-error'
         };
         const cacheControl = Object.keys(cacheHeaders)
-            .map(prop => resp[prop] && cacheHeaders[prop] + '=' + resp[prop])
+            .map(prop => Number.isInteger(resp[prop]) && cacheHeaders[prop] + '=' + resp[prop])
             .filter(val => !!val).join(', ');
 
         res.setHeader('Cache-Control', `${cacheControl}, public`);