diff --git a/checker/definition.go b/checker/definition.go
index c2fb6f5..31c996d 100644
--- a/checker/definition.go
+++ b/checker/definition.go
@@ -11,7 +11,7 @@ import (
 var Version = "built-in"
 
 // Definition returns the CheckerDefinition for the TLS checker.
-func Definition() *sdk.CheckerDefinition {
+func (p *tlsProvider) Definition() *sdk.CheckerDefinition {
 	return &sdk.CheckerDefinition{
 		ID:      "tls",
 		Name:    "TLS",
diff --git a/checker/prober.go b/checker/prober.go
index b528814..fcbe88d 100644
--- a/checker/prober.go
+++ b/checker/prober.go
@@ -33,7 +33,6 @@ func buildChain(certs []*x509.Certificate) []CertInfo {
 			DERBase64:     base64.StdEncoding.EncodeToString(c.Raw),
 			Subject:       c.Subject.String(),
 			Issuer:        c.Issuer.String(),
-			NotAfter:      c.NotAfter,
 			CertSHA256:    hex.EncodeToString(certSum256[:]),
 			CertSHA512:    hex.EncodeToString(certSum512[:]),
 			SPKISHA256:    hex.EncodeToString(spkiSum256[:]),
diff --git a/checker/types.go b/checker/types.go
index 58bd547..81e59bd 100644
--- a/checker/types.go
+++ b/checker/types.go
@@ -84,10 +84,6 @@ type CertInfo struct {
 	Subject string `json:"subject,omitempty"`
 	Issuer  string `json:"issuer,omitempty"`
 
-	// NotAfter is the certificate's expiry. Carried so editors can show
-	// "expires on …" without re-parsing the DER.
-	NotAfter time.Time `json:"not_after,omitempty"`
-
 	// Selector 0 = full certificate.
 	CertSHA256 string `json:"cert_sha256,omitempty"`
 	CertSHA512 string `json:"cert_sha512,omitempty"`