diff --git a/app/src/main/java/io/legado/app/ui/book/read/ReadBookScreen.kt b/app/src/main/java/io/legado/app/ui/book/read/ReadBookScreen.kt
index 795c93f4f..cc89c5049 100644
--- a/app/src/main/java/io/legado/app/ui/book/read/ReadBookScreen.kt
+++ b/app/src/main/java/io/legado/app/ui/book/read/ReadBookScreen.kt
@@ -444,16 +444,16 @@ fun ReadBookScreen(
         }
 
         is ReadBookSheet.ChangeBookSource -> {
-            val changeSourceSheet = state.activeSheet as? ReadBookSheet.ChangeBookSource
+            val changeSourceSheet = state.activeSheet
             val changeSourceBook = state.book
-            if (changeSourceSheet != null && changeSourceBook == null) {
+            if (changeSourceBook == null) {
                 LaunchedEffect(changeSourceSheet) {
                     onIntent(ReadBookIntent.DismissSheet)
                 }
             }
             if (changeSourceBook != null) {
                 ChangeSourceSheet(
-                    show = changeSourceSheet != null,
+                    show = true,
                     oldBook = changeSourceBook,
                     fromReadBookActivity = true,
                     allowAddAsNew = false,
diff --git a/app/src/main/java/io/legado/app/ui/config/themeConfig/ThemeConfigViewModel.kt b/app/src/main/java/io/legado/app/ui/config/themeConfig/ThemeConfigViewModel.kt
index 09ddd571c..27d8d7646 100644
--- a/app/src/main/java/io/legado/app/ui/config/themeConfig/ThemeConfigViewModel.kt
+++ b/app/src/main/java/io/legado/app/ui/config/themeConfig/ThemeConfigViewModel.kt
@@ -28,7 +28,10 @@ class ThemeConfigViewModel(
 ) : ViewModel() {
 
     val fontFolder = readSettingsRepository.preferences
-        .map { it.fontFolder as String? }
+        .map { preferences ->
+            val fontFolder: String? = preferences.fontFolder
+            fontFolder
+        }
         .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5000), null)
 
     fun setFontFolder(path: String) {