diff --git a/common/json_stream.c b/common/json_stream.c
index 60517b3fb..7d1cc92cb 100644
--- a/common/json_stream.c
+++ b/common/json_stream.c
@@ -372,6 +372,14 @@ void json_add_timeabs(struct json_stream *result, const char *fieldname,
 			       (u64)t.ts.tv_sec, (u64)t.ts.tv_nsec);
 }
 
+void json_add_timerel(struct json_stream *result, const char *fieldname,
+		      struct timerel t)
+{
+	json_add_primitive_fmt(result, fieldname,
+			       "%" PRIu64 ".%09" PRIu64,
+			       (u64)t.ts.tv_sec, (u64)t.ts.tv_nsec);
+}
+
 void json_add_timestr(struct json_stream *result, const char *fieldname,
 			  struct timespec ts)
 {
diff --git a/common/json_stream.h b/common/json_stream.h
index 9cc539e29..bfbb5d0a7 100644
--- a/common/json_stream.h
+++ b/common/json_stream.h
@@ -253,9 +253,14 @@ void json_add_hex_talarr(struct json_stream *result,
 			 const char *fieldname,
 			 const tal_t *data);
 
+/* '"fieldname" : 1749785122.000000001 */
 void json_add_timeabs(struct json_stream *result, const char *fieldname,
 		      struct timeabs t);
 
+/* '"fieldname" : 1.000000001 */
+void json_add_timerel(struct json_stream *result, const char *fieldname,
+		      struct timerel t);
+
 /* used in log.c and notification.c*/
 void json_add_timestr(struct json_stream *result, const char *fieldname,
 			  struct timespec ts);