diff --git a/server/scanner/BookScanner.js b/server/scanner/BookScanner.js
index 8ae616fe8..ade7260d9 100644
--- a/server/scanner/BookScanner.js
+++ b/server/scanner/BookScanner.js
@@ -136,12 +136,8 @@ class BookScanner {
 
       media.audioFiles = AudioFileScanner.runSmartTrackOrder(existingLibraryItem.relPath, media.audioFiles)
 
-      media.duration = 0
-      media.audioFiles.forEach((af) => {
-        if (!isNaN(af.duration)) {
-          media.duration += af.duration
-        }
-      })
+      // Recompute duration from included (non-excluded) tracks so disabled tracks don't get re-counted on rescan
+      media.updateDuration()
 
       media.changed('audioFiles', true)
     }
diff --git a/test/server/models/Book.test.js b/test/server/models/Book.test.js
new file mode 100644
index 000000000..162dbe92c
--- /dev/null
+++ b/test/server/models/Book.test.js
@@ -0,0 +1,62 @@
+const { expect } = require('chai')
+const { Sequelize } = require('sequelize')
+
+const Database = require('../../../server/Database')
+
+describe('Book', () => {
+  beforeEach(async () => {
+    global.ServerSettings = {}
+    Database.sequelize = new Sequelize({ dialect: 'sqlite', storage: ':memory:', logging: false })
+    Database.sequelize.uppercaseFirst = (str) => (str ? `${str[0].toUpperCase()}${str.substr(1)}` : '')
+    await Database.buildModels()
+  })
+
+  afterEach(async () => {
+    await Database.sequelize.sync({ force: true })
+  })
+
+  describe('updateDuration', () => {
+    it('sums only the included (non-excluded) audio files', () => {
+      const book = Database.bookModel.build({
+        title: 'Test Book',
+        duration: 0,
+        audioFiles: [
+          { ino: '1', duration: 100, exclude: false },
+          { ino: '2', duration: 50, exclude: true },
+          { ino: '3', duration: 25, exclude: false }
+        ]
+      })
+
+      const changed = book.updateDuration()
+
+      expect(book.duration).to.equal(125) // 100 + 25, the excluded 50 is ignored
+      expect(changed).to.be.true
+    })
+
+    it('returns false and leaves duration unchanged when already correct', () => {
+      const book = Database.bookModel.build({
+        title: 'Test Book',
+        duration: 100,
+        audioFiles: [{ ino: '1', duration: 100, exclude: false }]
+      })
+
+      expect(book.updateDuration()).to.be.false
+      expect(book.duration).to.equal(100)
+    })
+
+    it('ignores audio files with a non-numeric duration', () => {
+      const book = Database.bookModel.build({
+        title: 'Test Book',
+        duration: 0,
+        audioFiles: [
+          { ino: '1', duration: 100, exclude: false },
+          { ino: '2', duration: NaN, exclude: false }
+        ]
+      })
+
+      book.updateDuration()
+
+      expect(book.duration).to.equal(100)
+    })
+  })
+})