diff --git a/server.cpp b/server.cpp
index 659b15d..d654f5b 100644
--- a/server.cpp
+++ b/server.cpp
@@ -566,18 +566,21 @@ void server::handler()
 				if (ifr != IFR_OK && ifr != IFR_CONNECTION) {  // something wrong with the received PDU?
 					DOLOG(logging::ll_debug, "server::handler", endpoint, "invalid PDU");
 
-					is->iscsiInstSsnFormatErrors++;
-
 					std::optional<uint8_t> reason;
 
-					if (ifr == IFR_INVALID_FIELD || ifr == IFR_IO_ERROR || ifr == IFR_MISC)
+					if (ifr == IFR_INVALID_FIELD || ifr == IFR_IO_ERROR || ifr == IFR_MISC) {
+						is->iscsiInstSsnFormatErrors++;
 						reason = 0x09;
-					else if (ifr == IFR_DIGEST)
+					}
+					else if (ifr == IFR_DIGEST) {
+						is->iscsiInstSsnDigestErrors++;
 						reason = 0x02;
+					}
 					else if (ifr == IFR_INVALID_COMMAND)
 						reason = 0x05;
-					else
+					else {
 						DOLOG(logging::ll_error, "server::handler", endpoint, "internal error, IFR %d not known", ifr);
+					}
 
 					std::optional<blob_t> reject = generate_reject_pdu(*pdu, reason);
 					if (reject.has_value() == false) {
diff --git a/server.h b/server.h
index 58c5f4e..747f4fc 100644
--- a/server.h
+++ b/server.h
@@ -11,6 +11,7 @@ typedef struct
 	uint32_t iscsiSsnCmdPDUs;           // 1.3.6.1.2.1.142.1.10.2.1.1
 	uint32_t iscsiInstSsnFailures;      // 1.3.6.1.2.1.142.1.1.1.1.10
 	uint32_t iscsiInstSsnFormatErrors;  // 1.3.6.1.2.1.142.1.1.2.1.3
+	uint32_t iscsiInstSsnDigestErrors;  // 1.3.6.1.2.1.142.1.1.2.1.1
 	uint64_t iscsiSsnTxDataOctets;      // 1.3.6.1.2.1.142.1.10.2.1.3
 	uint64_t iscsiSsnRxDataOctets;      // 1.3.6.1.2.1.142.1.10.2.1.4
 	uint32_t iscsiTgtLoginAccepts;      // 1.3.6.1.2.1.142.1.6.2.1.1
diff --git a/snmp.cpp b/snmp.cpp
index e2a5a93..aa176d0 100644
--- a/snmp.cpp
+++ b/snmp.cpp
@@ -34,6 +34,7 @@ void init_snmp(snmp **const snmp_, snmp_data **const snmp_data_, io_stats_t *con
 	(*snmp_data_)->register_oid("1.3.6.1.2.1.142.1.10.2.1.1",   new snmp_data_type_stats_uint32_t(&is->iscsiSsnCmdPDUs));
 	(*snmp_data_)->register_oid("1.3.6.1.2.1.142.1.6.2.1.1",    new snmp_data_type_stats_uint32_t(&is->iscsiTgtLoginAccepts));
 	(*snmp_data_)->register_oid("1.3.6.1.2.1.142.1.6.3.1.1",    new snmp_data_type_stats_uint32_t(&is->iscsiTgtLogoutNormals));
+	(*snmp_data_)->register_oid("1.3.6.1.2.1.142.1.1.2.1.1",    new snmp_data_type_stats_uint32_t(&is->iscsiInstSsnDigestErrors));
 	(*snmp_data_)->register_oid("1.3.6.1.2.1.142.1.10.2.1.3",   new snmp_data_type_stats(snmp_integer::snmp_integer_type::si_counter64, &is->iscsiSsnTxDataOctets));
 	(*snmp_data_)->register_oid("1.3.6.1.2.1.142.1.10.2.1.4",   new snmp_data_type_stats(snmp_integer::snmp_integer_type::si_counter64, &is->iscsiSsnRxDataOctets));
 	(*snmp_data_)->register_oid("1.3.6.1.2.1.142.1.1.2.1.3",    new snmp_data_type_stats_uint32_t(&is->iscsiInstSsnFormatErrors));