diff --git a/main.go b/main.go
index 7fa4e99..a3a2ccf 100644
--- a/main.go
+++ b/main.go
@@ -333,7 +333,8 @@ func (br *bridge) publish(n *notification) error {
 		req.Header.Set("Actions", fmt.Sprintf("http, Silence, %s, method=POST, body=%s%s", url, n.silenceBody, authString))
 	}
 
-	configFingerprint := br.cfg.Ntfy.CertFingerprint
+	// hex.EncodeToString outputs a lower case string
+	configFingerprint := strings.ToLower(strings.ReplaceAll(br.cfg.Ntfy.CertFingerprint, ":", ""))
 	if configFingerprint != "" {
 		tlsCfg := &tls.Config{}
 		tlsCfg.VerifyPeerCertificate = func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {