diff --git a/api/src/resources/comment.rs b/api/src/resources/comment.rs
index e1998ca1..d5ca1df5 100644
--- a/api/src/resources/comment.rs
+++ b/api/src/resources/comment.rs
@@ -873,6 +873,7 @@ pub struct NewEntityWithSpan {
     pub name: EntityName,
     pub formatted_value: String,
     pub span: NewEntitySpan,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub field_id: Option<FieldId>,
 }
 
@@ -883,6 +884,7 @@ pub struct FieldId(pub String);
 pub struct NewEntityWithSpans {
     pub name: EntityName,
     pub formatted_value: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub field_id: Option<FieldId>,
     pub spans: Vec<NewEntitySpan>,
 }
@@ -900,6 +902,7 @@ pub struct Entity {
     pub name: EntityName,
     pub formatted_value: String,
     pub spans: Vec<EntitySpan>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub field_id: Option<FieldId>,
 }