diff --git a/.changeset/strong-candles-yell.md b/.changeset/strong-candles-yell.md
new file mode 100644
index 00000000..f17ea354
--- /dev/null
+++ b/.changeset/strong-candles-yell.md
@@ -0,0 +1,5 @@
+---
+"nostream": patch
+---
+
+Dedup keys were taking multiple tags, that was not according to NIP-01 behaviour.
diff --git a/migrations/20260419_140000_normalize_parameterized_deduplication.js b/migrations/20260419_140000_normalize_parameterized_deduplication.js
new file mode 100644
index 00000000..5be39f5c
--- /dev/null
+++ b/migrations/20260419_140000_normalize_parameterized_deduplication.js
@@ -0,0 +1,31 @@
+exports.up = async function (knex) {
+  await knex.raw(`
+    WITH ranked AS (
+      SELECT
+        id,
+        row_number() OVER (
+          PARTITION BY event_pubkey, event_kind, jsonb_build_array(COALESCE(event_deduplication->>0, ''))
+          ORDER BY event_created_at DESC, event_id ASC
+        ) AS row_rank
+      FROM events
+      WHERE event_kind >= 30000
+        AND event_kind < 40000
+    )
+    DELETE FROM events AS e
+    USING ranked AS r
+    WHERE e.id = r.id
+      AND r.row_rank > 1;
+  `)
+
+  await knex.raw(`
+    UPDATE events
+    SET event_deduplication = jsonb_build_array(COALESCE(event_deduplication->>0, ''))
+    WHERE event_kind >= 30000
+      AND event_kind < 40000
+      AND event_deduplication IS DISTINCT FROM jsonb_build_array(COALESCE(event_deduplication->>0, ''));
+  `)
+}
+
+exports.down = async function () {
+  // Irreversible data migration.
+}
diff --git a/src/services/event-import-service.ts b/src/services/event-import-service.ts
index 25e6df1c..d02d9e59 100644
--- a/src/services/event-import-service.ts
+++ b/src/services/event-import-service.ts
@@ -26,11 +26,11 @@ const enrichEventMetadata = (event: Event): Event => {
   }
 
   if (isParameterizedReplaceableEvent(event)) {
-    const [, ...deduplication] = event.tags.find((tag) => tag.length >= 2 && tag[0] === EventTags.Deduplication) ?? [
+    const [, deduplication] = event.tags.find((tag) => tag.length >= 2 && tag[0] === EventTags.Deduplication) ?? [
       null,
       '',
     ]
-    enriched = { ...enriched, [EventDeduplicationMetadataKey]: deduplication }
+    enriched = { ...enriched, [EventDeduplicationMetadataKey]: deduplication ? [deduplication] : [''] }
   }
 
   return enriched as Event
diff --git a/test/unit/services/event-import-service.spec.ts b/test/unit/services/event-import-service.spec.ts
index 2f67eded..3c3cd590 100644
--- a/test/unit/services/event-import-service.spec.ts
+++ b/test/unit/services/event-import-service.spec.ts
@@ -3,7 +3,13 @@ import { join } from 'path'
 import fs from 'fs'
 import os from 'os'
 
-import { EventImportLineError, EventImportService, EventImportStats } from '../../../src/services/event-import-service'
+import {
+  createEventBatchPersister,
+  EventImportLineError,
+  EventImportService,
+  EventImportStats,
+} from '../../../src/services/event-import-service'
+import { EventDeduplicationMetadataKey, EventKinds, EventTags } from '../../../src/constants/base'
 import { Event } from '../../../src/@types/event'
 import { expect } from 'chai'
 import { getEvents } from '../data/events'
@@ -170,4 +176,36 @@ describe('EventImportService', () => {
       expect(lineErrors.length).to.equal(0)
     }
   })
+
+  it('normalizes parameterized replaceable deduplication to first d tag value', async () => {
+    const parameterizedEvent: Event = {
+      id: 'a'.repeat(64),
+      pubkey: 'b'.repeat(64),
+      created_at: 1,
+      kind: EventKinds.PARAMETERIZED_REPLACEABLE_FIRST,
+      tags: [[EventTags.Deduplication, 'one', 'two']],
+      content: 'hello',
+      sig: 'c'.repeat(128),
+    }
+
+    let upsertedEvents: Event[] = []
+
+    const eventRepository = {
+      create: async () => 0,
+      createMany: async () => 0,
+      upsert: async () => 0,
+      upsertMany: async (events: Event[]) => {
+        upsertedEvents = events
+        return events.length
+      },
+      deleteByPubkeyAndIds: async () => 0,
+    } as any
+
+    const persistBatch = createEventBatchPersister(eventRepository)
+    const inserted = await persistBatch([parameterizedEvent])
+
+    expect(inserted).to.equal(1)
+    expect(upsertedEvents).to.have.length(1)
+    expect((upsertedEvents[0] as any)[EventDeduplicationMetadataKey]).to.deep.equal(['one'])
+  })
 })