diff --git a/sys/dev/iscsi/iscsi.c b/sys/dev/iscsi/iscsi.c
index eba365f7ad3e..9f49db2ad935 100644
--- a/sys/dev/iscsi/iscsi.c
+++ b/sys/dev/iscsi/iscsi.c
@@ -892,15 +892,39 @@ iscsi_pdu_handle_scsi_response(struct icl_pdu *response)
 	}
 
 	ccb = io->io_ccb;
-	if (ntohl(bhssr->bhssr_expdatasn) != io->io_datasn) {
-		ISCSI_SESSION_WARN(is,
-		    "ExpDataSN mismatch in SCSI Response (%u vs %u)",
-		    ntohl(bhssr->bhssr_expdatasn), io->io_datasn);
-		icl_pdu_free(response);
-		iscsi_session_reconnect(is);
-		ISCSI_SESSION_UNLOCK(is);
-		return;
+	if (bhssr->bhssr_response == BHSSR_RESPONSE_COMMAND_COMPLETED) {
+		if (ntohl(bhssr->bhssr_expdatasn) != io->io_datasn) {
+			ISCSI_SESSION_WARN(is,
+			    "ExpDataSN mismatch in SCSI Response (%u vs %u)",
+			    ntohl(bhssr->bhssr_expdatasn), io->io_datasn);
+
+			/*
+			 * XXX: Permit an ExpDataSN of zero for errors.
+			 *
+			 * This doesn't conform to RFC 7143, but some
+			 * targets seem to do this.
+			 */
+			if (bhssr->bhssr_status != 0 &&
+			    bhssr->bhssr_expdatasn == htonl(0))
+				goto skip_expdatasn;
+
+			icl_pdu_free(response);
+			iscsi_session_reconnect(is);
+			ISCSI_SESSION_UNLOCK(is);
+			return;
+		}
+	} else {
+		if (bhssr->bhssr_expdatasn != htonl(0)) {
+			ISCSI_SESSION_WARN(is,
+			    "ExpDataSN mismatch in SCSI Response (%u vs 0)",
+			    ntohl(bhssr->bhssr_expdatasn));
+			icl_pdu_free(response);
+			iscsi_session_reconnect(is);
+			ISCSI_SESSION_UNLOCK(is);
+			return;
+		}
 	}
+skip_expdatasn:
 
 	/*
 	 * With iSER, after getting good response we can be sure