diff --git a/capture/src/api.rs b/capture/src/api.rs
index 91ed578..8e595fc 100644
--- a/capture/src/api.rs
+++ b/capture/src/api.rs
@@ -87,7 +87,10 @@ pub struct ProcessedEvent {
     pub ip: String,
     pub data: String,
     pub now: String,
-    #[serde(with = "time::serde::rfc3339::option")]
+    #[serde(
+        with = "time::serde::rfc3339::option",
+        skip_serializing_if = "Option::is_none"
+    )]
     pub sent_at: Option<OffsetDateTime>,
     pub token: String,
 }