diff --git a/src/servers/src/prom_row_builder.rs b/src/servers/src/prom_row_builder.rs
index 20a049f472..9bfdd02182 100644
--- a/src/servers/src/prom_row_builder.rs
+++ b/src/servers/src/prom_row_builder.rs
@@ -28,7 +28,7 @@ use crate::proto::PromLabel;
 use crate::repeated_field::Clear;
 
 /// [TablesBuilder] serves as an intermediate container to build [RowInsertRequests].
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub(crate) struct TablesBuilder {
     tables: HashMap<String, TableBuilder>,
 }
@@ -68,6 +68,7 @@ impl TablesBuilder {
 }
 
 /// Builder for one table.
+#[derive(Debug)]
 pub(crate) struct TableBuilder {
     /// Column schemas.
     schema: Vec<ColumnSchema>,
diff --git a/src/servers/src/proto.rs b/src/servers/src/proto.rs
index 1a96cd9ed8..906a7ff52a 100644
--- a/src/servers/src/proto.rs
+++ b/src/servers/src/proto.rs
@@ -26,10 +26,13 @@ use crate::prom_store::METRIC_NAME_LABEL_BYTES;
 use crate::repeated_field::{Clear, RepeatedField};
 
 impl Clear for Sample {
-    fn clear(&mut self) {}
+    fn clear(&mut self) {
+        self.timestamp = 0;
+        self.value = 0.0;
+    }
 }
 
-#[derive(Default, Clone)]
+#[derive(Default, Clone, Debug)]
 pub struct PromLabel {
     pub name: Bytes,
     pub value: Bytes,
@@ -76,7 +79,7 @@ impl PromLabel {
     }
 }
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct PromTimeSeries {
     pub table_name: String,
     pub labels: RepeatedField<PromLabel>,
@@ -161,7 +164,7 @@ impl PromTimeSeries {
     }
 }
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct PromWriteRequest {
     table_data: TablesBuilder,
     series: PromTimeSeries,