diff --git a/src/keys.js b/src/keys.js
index 89bcc2a..0c97149 100644
--- a/src/keys.js
+++ b/src/keys.js
@@ -283,7 +283,7 @@ const process = async (publicKey) => {
     }
 
     if ('selfCertifications' in user && user.selfCertifications.length > 0) {
-      const selfCertification = user.selfCertifications.sort((e1, e2) => e2.created - e1.created)[0]
+      const selfCertification = user.selfCertifications.sort((e1, e2) => e2.created.getTime() - e1.created.getTime())[0]
 
       const notations = selfCertification.rawNotations
       usersOutput[i].claims = notations
diff --git a/src/verifications.js b/src/verifications.js
index 25fda91..dc1050e 100644
--- a/src/verifications.js
+++ b/src/verifications.js
@@ -151,7 +151,7 @@ const containsProof = async (data, params) => {
         method: 'HEAD'
       })
         .catch(e => {
-          return false
+          return undefined
         })
 
       if (!response) continue