diff --git a/server/subsonic/album_lists.go b/server/subsonic/album_lists.go
index 18c664b6f..56cf469c5 100644
--- a/server/subsonic/album_lists.go
+++ b/server/subsonic/album_lists.go
@@ -63,7 +63,10 @@ func (api *Router) getAlbumList(r *http.Request) (model.Albums, int64, error) {
 	}
 
 	// Get optional library IDs from musicFolderId parameter
-	musicFolderIds, _ := selectedMusicFolderIds(r, false)
+	musicFolderIds, err := selectedMusicFolderIds(r, false)
+	if err != nil {
+		return nil, 0, err
+	}
 	opts = filter.ApplyLibraryFilter(opts, musicFolderIds)
 
 	opts.Offset = p.IntOr("offset", 0)
@@ -118,7 +121,10 @@ func (api *Router) getStarredItems(r *http.Request) (model.Artists, model.Albums
 	ctx := r.Context()
 
 	// Get optional library IDs from musicFolderId parameter
-	musicFolderIds, _ := selectedMusicFolderIds(r, false)
+	musicFolderIds, err := selectedMusicFolderIds(r, false)
+	if err != nil {
+		return nil, nil, nil, err
+	}
 
 	// Prepare variables to capture results from parallel execution
 	var artists model.Artists
@@ -126,7 +132,7 @@ func (api *Router) getStarredItems(r *http.Request) (model.Artists, model.Albums
 	var mediaFiles model.MediaFiles
 
 	// Execute all three queries in parallel for better performance
-	err := run.Parallel(
+	err = run.Parallel(
 		// Query starred artists
 		func() error {
 			artistOpts := filter.ApplyArtistLibraryFilter(filter.ArtistsByStarred(), musicFolderIds)
@@ -226,7 +232,10 @@ func (api *Router) GetRandomSongs(r *http.Request) (*responses.Subsonic, error)
 	toYear := p.IntOr("toYear", 0)
 
 	// Get optional library IDs from musicFolderId parameter
-	musicFolderIds, _ := selectedMusicFolderIds(r, false)
+	musicFolderIds, err := selectedMusicFolderIds(r, false)
+	if err != nil {
+		return nil, err
+	}
 	opts := filter.SongsByRandom(genre, fromYear, toYear)
 	opts = filter.ApplyLibraryFilter(opts, musicFolderIds)
 
@@ -249,7 +258,10 @@ func (api *Router) GetSongsByGenre(r *http.Request) (*responses.Subsonic, error)
 	genre, _ := p.String("genre")
 
 	// Get optional library IDs from musicFolderId parameter
-	musicFolderIds, _ := selectedMusicFolderIds(r, false)
+	musicFolderIds, err := selectedMusicFolderIds(r, false)
+	if err != nil {
+		return nil, err
+	}
 	opts := filter.ByGenre(genre)
 	opts = filter.ApplyLibraryFilter(opts, musicFolderIds)
 
diff --git a/server/subsonic/helpers.go b/server/subsonic/helpers.go
index 70a85bc57..f9733bb3f 100644
--- a/server/subsonic/helpers.go
+++ b/server/subsonic/helpers.go
@@ -486,7 +486,7 @@ func getUserAccessibleLibraries(ctx context.Context) []model.Library {
 // selectedMusicFolderIds retrieves the music folder IDs from the request parameters.
 // If no IDs are provided, it returns all libraries the user has access to (based on the user found in the context).
 // If the parameter is required and not present, it returns an error.
-// Invalid library IDs (those the user doesn't have access to) are silently filtered out.
+// If any of the provided library IDs are invalid (don't exist or user doesn't have access), returns ErrorDataNotFound.
 func selectedMusicFolderIds(r *http.Request, required bool) ([]int, error) {
 	p := req.Params(r)
 	musicFolderIds, err := p.Ints("musicFolderId")
@@ -501,14 +501,13 @@ func selectedMusicFolderIds(r *http.Request, required bool) ([]int, error) {
 	accessibleLibraryIds := slice.Map(libraries, func(lib model.Library) int { return lib.ID })
 
 	if len(musicFolderIds) > 0 {
-		// Validate and filter out invalid library IDs
-		validIds := make([]int, 0, len(musicFolderIds))
+		// Validate all provided library IDs - if any are invalid, return an error
 		for _, id := range musicFolderIds {
-			if slices.Contains(accessibleLibraryIds, id) {
-				validIds = append(validIds, id)
+			if !slices.Contains(accessibleLibraryIds, id) {
+				return nil, newError(responses.ErrorDataNotFound, "Library %d not found or not accessible", id)
 			}
 		}
-		return validIds, nil
+		return musicFolderIds, nil
 	}
 
 	// If no musicFolderId is provided, return all libraries the user has access to.
diff --git a/server/subsonic/helpers_test.go b/server/subsonic/helpers_test.go
index 2f388217a..a6508d4bb 100644
--- a/server/subsonic/helpers_test.go
+++ b/server/subsonic/helpers_test.go
@@ -204,22 +204,14 @@ var _ = Describe("helpers", func() {
 				Expect(ids).To(Equal([]int{2})) // Only valid ID is returned
 			})
 
-			It("should filter out library IDs the user doesn't have access to", func() {
+			It("should return error when any library ID is not accessible", func() {
 				r := httptest.NewRequest("GET", "/test?musicFolderId=1&musicFolderId=5&musicFolderId=2&musicFolderId=99", nil)
 				r = r.WithContext(ctx)
 
 				ids, err := selectedMusicFolderIds(r, false)
-				Expect(err).ToNot(HaveOccurred())
-				Expect(ids).To(Equal([]int{1, 2})) // Only accessible libraries (1, 2) are returned, 5 and 99 are filtered out
-			})
-
-			It("should return empty slice when user has no access to any of the requested libraries", func() {
-				r := httptest.NewRequest("GET", "/test?musicFolderId=99&musicFolderId=100", nil)
-				r = r.WithContext(ctx)
-
-				ids, err := selectedMusicFolderIds(r, false)
-				Expect(err).ToNot(HaveOccurred())
-				Expect(ids).To(Equal([]int{})) // No accessible libraries in the request
+				Expect(err).To(HaveOccurred())
+				Expect(err.Error()).To(ContainSubstring("Library 5 not found or not accessible"))
+				Expect(ids).To(BeNil())
 			})
 		})