diff --git a/backend/mlarchive/utils/jsonlogger.py b/backend/mlarchive/utils/jsonlogger.py
index 057b97c0..a0e5ffd3 100644
--- a/backend/mlarchive/utils/jsonlogger.py
+++ b/backend/mlarchive/utils/jsonlogger.py
@@ -31,3 +31,4 @@ def add_fields(self, log_record, record, message_dict):
         log_record.setdefault("cf_connecting_ip", record.args["{cf-connecting-ip}i"])
         log_record.setdefault("cf_connecting_ipv6", record.args["{cf-connecting-ipv6}i"])
         log_record.setdefault("cf_ray", record.args["{cf-ray}i"])
+        log_record.setdefault("asn", record.args["{x-ip-src-asnum}i"])
diff --git a/k8s/nginx-logging.conf b/k8s/nginx-logging.conf
index 3c4ade46..0bc7deca 100644
--- a/k8s/nginx-logging.conf
+++ b/k8s/nginx-logging.conf
@@ -1,4 +1,6 @@
-# Define JSON log format - must be loaded before config that references it
+# Define JSON log format - must be loaded before config that references it.
+# Note that each line is fully enclosed in single quotes. Commas in arrays are
+# intentionally inside the single quotes.
 log_format  ietfjson  escape=json
   '{'
     '"time":"$${keepempty}time_iso8601",'
@@ -16,5 +18,6 @@ log_format  ietfjson  escape=json
     '"x_forwarded_proto":"$${keepempty}http_x_forwarded_proto",'
     '"cf_connecting_ip":"$${keepempty}http_cf_connecting_ip",'
     '"cf_connecting_ipv6":"$${keepempty}http_cf_connecting_ipv6",'
-    '"cf_ray":"$${keepempty}http_cf_ray"'
+    '"cf_ray":"$${keepempty}http_cf_ray",'
+    '"asn":"$${keepempty}http_x_ip_src_asnum"'
   '}';