diff --git a/change/@apibara-beaconchain-7b39a030-0724-44c0-8cec-7300e5efa49b.json b/change/@apibara-beaconchain-7b39a030-0724-44c0-8cec-7300e5efa49b.json
new file mode 100644
index 00000000..56c9f2fc
--- /dev/null
+++ b/change/@apibara-beaconchain-7b39a030-0724-44c0-8cec-7300e5efa49b.json
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "plugins: fix issue caused by cursors with empty unique key",
+  "packageName": "@apibara/beaconchain",
+  "email": "francesco@ceccon.me",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@apibara-evm-c96dd7a5-d16a-44aa-ac3a-947a9b904517.json b/change/@apibara-evm-c96dd7a5-d16a-44aa-ac3a-947a9b904517.json
new file mode 100644
index 00000000..f2130ec2
--- /dev/null
+++ b/change/@apibara-evm-c96dd7a5-d16a-44aa-ac3a-947a9b904517.json
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "plugins: fix issue caused by cursors with empty unique key",
+  "packageName": "@apibara/evm",
+  "email": "francesco@ceccon.me",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@apibara-plugin-drizzle-c4aaf5bc-24c6-4883-9b29-cf614279c5db.json b/change/@apibara-plugin-drizzle-c4aaf5bc-24c6-4883-9b29-cf614279c5db.json
new file mode 100644
index 00000000..e7a10899
--- /dev/null
+++ b/change/@apibara-plugin-drizzle-c4aaf5bc-24c6-4883-9b29-cf614279c5db.json
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "plugin-drizzle: fix issue caused by cursors with empty unique key",
+  "packageName": "@apibara/plugin-drizzle",
+  "email": "francesco@ceccon.me",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@apibara-plugin-mongo-ddb9c304-419b-4291-bb27-6c198e0501cd.json b/change/@apibara-plugin-mongo-ddb9c304-419b-4291-bb27-6c198e0501cd.json
new file mode 100644
index 00000000..b9a7c820
--- /dev/null
+++ b/change/@apibara-plugin-mongo-ddb9c304-419b-4291-bb27-6c198e0501cd.json
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "plugins: fix issue caused by cursors with empty unique key",
+  "packageName": "@apibara/plugin-mongo",
+  "email": "francesco@ceccon.me",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@apibara-plugin-sqlite-ab552e08-0770-4528-b9a9-f1ffb9e0105f.json b/change/@apibara-plugin-sqlite-ab552e08-0770-4528-b9a9-f1ffb9e0105f.json
new file mode 100644
index 00000000..99965cd8
--- /dev/null
+++ b/change/@apibara-plugin-sqlite-ab552e08-0770-4528-b9a9-f1ffb9e0105f.json
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "plugins: fix issue caused by cursors with empty unique key",
+  "packageName": "@apibara/plugin-sqlite",
+  "email": "francesco@ceccon.me",
+  "dependentChangeType": "patch"
+}
diff --git a/change/@apibara-protocol-c3b43226-48fe-4e9f-abe7-760ca8e09b82.json b/change/@apibara-protocol-c3b43226-48fe-4e9f-abe7-760ca8e09b82.json
new file mode 100644
index 00000000..4056d7bd
--- /dev/null
+++ b/change/@apibara-protocol-c3b43226-48fe-4e9f-abe7-760ca8e09b82.json
@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "plugins: fix issue caused by cursors with empty unique key",
+  "packageName": "@apibara/protocol",
+  "email": "francesco@ceccon.me",
+  "dependentChangeType": "patch"
+}
diff --git a/package.json b/package.json
index 32e7caa7..87f4dce5 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,10 @@
           "packages/evm",
           "packages/indexer",
           "packages/protocol",
-          "packages/starknet"
+          "packages/starknet",
+          "packages/plugin-drizzle",
+          "packages/plugin-mongo",
+          "packages/plugin-sqlite"
         ]
       }
     ],
diff --git a/packages/beaconchain/package.json b/packages/beaconchain/package.json
index 78799b62..e22e6d6a 100644
--- a/packages/beaconchain/package.json
+++ b/packages/beaconchain/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@apibara/beaconchain",
-  "version": "2.0.1-beta.31",
+  "version": "2.0.1-beta.39",
   "type": "module",
   "files": [
     "dist",
diff --git a/packages/evm/package.json b/packages/evm/package.json
index 172c63ab..bd710518 100644
--- a/packages/evm/package.json
+++ b/packages/evm/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@apibara/evm",
-  "version": "2.0.1-beta.31",
+  "version": "2.0.1-beta.39",
   "type": "module",
   "files": [
     "dist",
diff --git a/packages/plugin-drizzle/package.json b/packages/plugin-drizzle/package.json
index 73445745..eb4e5500 100644
--- a/packages/plugin-drizzle/package.json
+++ b/packages/plugin-drizzle/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@apibara/plugin-drizzle",
-  "version": "2.0.0-beta.38",
+  "version": "2.0.0-beta.39",
   "type": "module",
   "files": [
     "dist",
diff --git a/packages/plugin-drizzle/src/persistence.ts b/packages/plugin-drizzle/src/persistence.ts
index 2a88c1a2..8e1fddb8 100644
--- a/packages/plugin-drizzle/src/persistence.ts
+++ b/packages/plugin-drizzle/src/persistence.ts
@@ -1,4 +1,4 @@
-import type { Cursor } from "@apibara/protocol";
+import { type Cursor, normalizeCursor } from "@apibara/protocol";
 import { and, eq, gt, isNull, lt } from "drizzle-orm";
 import type {
   ExtractTablesWithRelations,
@@ -15,10 +15,7 @@ const SCHEMA_VERSION_TABLE_NAME = "__indexer_schema_version";
 export const checkpoints = pgTable(CHECKPOINTS_TABLE_NAME, {
   id: text("id").notNull().primaryKey(),
   orderKey: integer("order_key").notNull(),
-  uniqueKey: text("unique_key")
-    .$type<`0x${string}` | undefined>()
-    .notNull()
-    .default(undefined),
+  uniqueKey: text("unique_key"),
 });
 
 export const filters = pgTable(
@@ -87,7 +84,7 @@ export async function initializePersistentState<
         CREATE TABLE IF NOT EXISTS ${CHECKPOINTS_TABLE_NAME} (
           id TEXT PRIMARY KEY,
           order_key INTEGER NOT NULL,
-          unique_key TEXT NOT NULL DEFAULT ''
+          unique_key TEXT
         );
       `);
 
@@ -212,10 +209,10 @@ export async function getState<
       .where(eq(checkpoints.id, indexerId));
 
     const cursor = checkpointRows[0]
-      ? {
+      ? normalizeCursor({
           orderKey: BigInt(checkpointRows[0].orderKey),
           uniqueKey: checkpointRows[0].uniqueKey,
-        }
+        })
       : undefined;
 
     const filterRows = await tx
diff --git a/packages/plugin-drizzle/tests/storage.test.ts b/packages/plugin-drizzle/tests/storage.test.ts
index 956aadf9..2b8ab56f 100644
--- a/packages/plugin-drizzle/tests/storage.test.ts
+++ b/packages/plugin-drizzle/tests/storage.test.ts
@@ -680,7 +680,7 @@ describe("Drizzle test", () => {
         {
           "id": "indexer_testing_default",
           "orderKey": 5000005,
-          "uniqueKey": "",
+          "uniqueKey": null,
         },
       ]
     `);
@@ -846,7 +846,7 @@ describe("Drizzle test", () => {
         {
           "id": "indexer_testing_default",
           "orderKey": 108,
-          "uniqueKey": "",
+          "uniqueKey": null,
         },
       ]
     `);
@@ -1030,7 +1030,7 @@ describe("Drizzle test", () => {
         {
           "id": "indexer_testing_default",
           "orderKey": 107,
-          "uniqueKey": "",
+          "uniqueKey": null,
         },
       ]
     `);
@@ -1206,7 +1206,7 @@ describe("Drizzle test", () => {
         {
           "id": "indexer_testing_default",
           "orderKey": 107,
-          "uniqueKey": "",
+          "uniqueKey": null,
         },
       ]
     `);
diff --git a/packages/plugin-mongo/src/persistence.ts b/packages/plugin-mongo/src/persistence.ts
index c632fc63..d0b25ac4 100644
--- a/packages/plugin-mongo/src/persistence.ts
+++ b/packages/plugin-mongo/src/persistence.ts
@@ -1,10 +1,10 @@
-import type { Cursor } from "@apibara/protocol";
+import { type Cursor, normalizeCursor } from "@apibara/protocol";
 import type { ClientSession, Db } from "mongodb";
 
 export type CheckpointSchema = {
   id: string;
   orderKey: number;
-  uniqueKey?: `0x${string}`;
+  uniqueKey: string | null;
 };
 
 export type FilterSchema = {
@@ -98,10 +98,10 @@ export async function getState<TFilter>(props: {
     .findOne({ id: indexerId }, { session });
 
   if (checkpointRow) {
-    cursor = {
+    cursor = normalizeCursor({
       orderKey: BigInt(checkpointRow.orderKey),
       uniqueKey: checkpointRow.uniqueKey,
-    };
+    });
   }
 
   const filterRow = await db
diff --git a/packages/plugin-mongo/tests/storage.test.ts b/packages/plugin-mongo/tests/storage.test.ts
index d05c5b3c..7ef79230 100644
--- a/packages/plugin-mongo/tests/storage.test.ts
+++ b/packages/plugin-mongo/tests/storage.test.ts
@@ -427,7 +427,6 @@ describe("MongoDB Test", () => {
         {
           "cursor": {
             "orderKey": 5000005n,
-            "uniqueKey": null,
           },
           "filter": undefined,
         }
diff --git a/packages/plugin-sqlite/package.json b/packages/plugin-sqlite/package.json
index 0f15a45d..3826a12f 100644
--- a/packages/plugin-sqlite/package.json
+++ b/packages/plugin-sqlite/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@apibara/plugin-sqlite",
-  "version": "2.0.0-beta.38",
+  "version": "2.0.0-beta.39",
   "type": "module",
   "files": [
     "dist",
diff --git a/packages/plugin-sqlite/src/persistence.ts b/packages/plugin-sqlite/src/persistence.ts
index fd191bb3..37e3736b 100644
--- a/packages/plugin-sqlite/src/persistence.ts
+++ b/packages/plugin-sqlite/src/persistence.ts
@@ -1,4 +1,4 @@
-import type { Cursor } from "@apibara/protocol";
+import { type Cursor, normalizeCursor } from "@apibara/protocol";
 import type { Database } from "better-sqlite3";
 
 import { assertInTransaction, deserialize, serialize } from "./utils";
@@ -57,10 +57,10 @@ export function getState<TFilter>(props: {
   let filter: TFilter | undefined;
 
   if (storedCursor?.order_key) {
-    cursor = {
+    cursor = normalizeCursor({
       orderKey: BigInt(storedCursor.order_key),
-      uniqueKey: storedCursor.unique_key as `0x${string}`,
-    };
+      uniqueKey: storedCursor.unique_key ? storedCursor.unique_key : null,
+    });
   }
 
   if (storedFilter) {
diff --git a/packages/protocol/src/common.ts b/packages/protocol/src/common.ts
index fceb35b5..c76c2046 100644
--- a/packages/protocol/src/common.ts
+++ b/packages/protocol/src/common.ts
@@ -67,3 +67,27 @@ export const cursorFromBytes = Schema.decodeSync(CursorFromBytes);
 export function isCursor(value: unknown): value is Cursor {
   return Schema.is(Cursor)(value);
 }
+
+/** Normalize a cursor.
+ *
+ * The challenge is that the `Cursor` validator expects `uniqueKey` to be either a `0x${string}`
+ * or not present at all. Setting the field to `undefined` will result in a validation error.
+ *
+ * @param cursor The cursor to normalize
+ */
+export function normalizeCursor(cursor: {
+  orderKey: bigint;
+  uniqueKey: string | null;
+}): Cursor {
+  if (cursor.uniqueKey !== null && cursor.uniqueKey.length > 0) {
+    const uniqueKey = cursor.uniqueKey as `0x${string}`;
+    return {
+      orderKey: BigInt(cursor.orderKey),
+      uniqueKey,
+    };
+  }
+
+  return {
+    orderKey: BigInt(cursor.orderKey),
+  };
+}