diff --git a/library.c b/library.c
index 12d48fcd..2f0392b6 100644
--- a/library.c
+++ b/library.c
@@ -1031,7 +1031,7 @@ const char *openconnect_get_cstp_cipher(struct openconnect_info *vpninfo)
 const char *openconnect_get_peer_cert_hash(struct openconnect_info *vpninfo)
 {
 	if (vpninfo->peer_cert_hash == NULL)
-		vpninfo->peer_cert_hash = openconnect_bin2hex("sha256:", vpninfo->peer_cert_sha256_raw, sizeof(vpninfo->peer_cert_sha256_raw));
+		vpninfo->peer_cert_hash = openconnect_bin2base64("pin-sha256:", vpninfo->peer_cert_sha256_raw, sizeof(vpninfo->peer_cert_sha256_raw));
 	return vpninfo->peer_cert_hash;
 }