diff --git a/packages/api/src/generated/graphql.ts b/packages/api/src/generated/graphql.ts
index b72113048..f0f41ff68 100644
--- a/packages/api/src/generated/graphql.ts
+++ b/packages/api/src/generated/graphql.ts
@@ -2093,7 +2093,7 @@ export enum SaveArticleReadingProgressErrorCode {
 
 export type SaveArticleReadingProgressInput = {
   id: Scalars['ID'];
-  readingProgressAnchorIndex: Scalars['Int'];
+  readingProgressAnchorIndex?: InputMaybe<Scalars['Int']>;
   readingProgressPercent: Scalars['Float'];
   readingProgressTopPercent?: InputMaybe<Scalars['Float']>;
 };
diff --git a/packages/api/src/generated/schema.graphql b/packages/api/src/generated/schema.graphql
index b70838275..3ef33f886 100644
--- a/packages/api/src/generated/schema.graphql
+++ b/packages/api/src/generated/schema.graphql
@@ -1572,7 +1572,7 @@ enum SaveArticleReadingProgressErrorCode {
 
 input SaveArticleReadingProgressInput {
   id: ID!
-  readingProgressAnchorIndex: Int!
+  readingProgressAnchorIndex: Int
   readingProgressPercent: Float!
   readingProgressTopPercent: Float
 }
diff --git a/packages/api/src/resolvers/article/index.ts b/packages/api/src/resolvers/article/index.ts
index 995f3b584..cfc3898cd 100644
--- a/packages/api/src/resolvers/article/index.ts
+++ b/packages/api/src/resolvers/article/index.ts
@@ -581,7 +581,7 @@ export const saveArticleReadingProgressResolver = authorized<
       (readingProgressTopPercent &&
         (readingProgressTopPercent < 0 ||
           readingProgressTopPercent > readingProgressPercent)) ||
-      readingProgressAnchorIndex < 0
+      (readingProgressAnchorIndex && readingProgressAnchorIndex < 0)
     ) {
       return { errorCodes: [SaveArticleReadingProgressErrorCode.BadData] }
     }
@@ -609,7 +609,7 @@ export const saveArticleReadingProgressResolver = authorized<
         readingProgressAnchorIndex === 0
           ? 0
           : Math.max(
-              readingProgressAnchorIndex,
+              readingProgressAnchorIndex || 0,
               libraryItem.readingProgressHighestReadAnchor
             ),
       readingProgressTopPercent: readingProgressTopPercentToSave,
diff --git a/packages/api/src/schema.ts b/packages/api/src/schema.ts
index 14e257fd3..e3b2b3442 100755
--- a/packages/api/src/schema.ts
+++ b/packages/api/src/schema.ts
@@ -636,7 +636,7 @@ const schema = gql`
     id: ID!
     readingProgressTopPercent: Float
     readingProgressPercent: Float!
-    readingProgressAnchorIndex: Int!
+    readingProgressAnchorIndex: Int
   }
   enum SaveArticleReadingProgressErrorCode {
     NOT_FOUND