diff --git a/modules/m_challenge.c b/modules/m_challenge.c
index 92f19d3..9a00607 100644
--- a/modules/m_challenge.c
+++ b/modules/m_challenge.c
@@ -237,6 +237,25 @@ m_challenge(struct Client *client_p, struct Client *source_p, int parc, const ch
 		return 0;
 	}
 
+	if (oper_p->certfp != NULL)
+	{
+		if (source_p->certfp == NULL || strcasecmp(source_p->certfp, oper_p->certfp))
+		{
+			sendto_one_numeric(source_p, ERR_NOOPERHOST, form_str(ERR_NOOPERHOST));
+			ilog(L_FOPER, "FAILED OPER (%s) by (%s!%s@%s) (%s) -- client certificate fingerprint mismatch",
+			     name, source_p->name,
+			     source_p->username, source_p->host, source_p->sockhost);
+
+			if(ConfigFileEntry.failed_oper_notice)
+			{
+				sendto_realops_snomask(SNO_GENERAL, L_ALL,
+						     "Failed OPER attempt - client certificate fingerprint mismatch by %s (%s@%s)",
+						     source_p->name, source_p->username, source_p->host);
+			}
+			return 0;
+		}
+	}
+
 	if(!generate_challenge(&challenge, &(source_p->localClient->challenge), oper_p->rsa_pubkey))
 	{
 		char *chal = challenge;