we have no declaration of usmHMACMD5AuthProtocol

diff --git a/src/libs/zbxpoller/checks_snmp.c b/src/libs/zbxpoller/checks_snmp.c
index b335351..2734f51 100644
--- a/src/libs/zbxpoller/checks_snmp.c
+++ b/src/libs/zbxpoller/checks_snmp.c
@@ -685,10 +685,12 @@ static int	zbx_snmpv3_set_auth_protocol(unsigned char snmpv3_authprotocol, struc
 
 	switch (snmpv3_authprotocol)
 	{
+#ifndef NETSNMP_DISABLE_MD5
 		case ITEM_SNMPV3_AUTHPROTOCOL_MD5:
 			session->securityAuthProto = usmHMACMD5AuthProtocol;
 			session->securityAuthProtoLen = USM_AUTH_PROTO_MD5_LEN;
 			break;
+#endif
 		case ITEM_SNMPV3_AUTHPROTOCOL_SHA1:
 			session->securityAuthProto = usmHMACSHA1AuthProtocol;
 			session->securityAuthProtoLen = USM_AUTH_PROTO_SHA_LEN;