diff --git a/engines/stark/services/diary.h b/engines/stark/services/diary.h
index 617f5cc2244..ac3b5f5c8b8 100644
--- a/engines/stark/services/diary.h
+++ b/engines/stark/services/diary.h
@@ -84,16 +84,16 @@ public:
 
 	/** Get info of added FMV entries */
 	uint countFMV() const { return _fmvEntries.size(); }
-	Common::String &getFMVFilename(uint index) { return _fmvEntries[index].filename; }
-	Common::String &getFMVTitle(uint index) { return _fmvEntries[index].title; }
+	const Common::String &getFMVFilename(uint index) const { return _fmvEntries[index].filename; }
+	const Common::String &getFMVTitle(uint index) const { return _fmvEntries[index].title; }
 
 	/** Get info of added Diary entries */
 	uint countDiary() const { return _diaryEntries.size(); }
-	Common::String &getDiary(uint index) { return _diaryEntries[index]; }
+	const Common::String &getDiary(uint index) const { return _diaryEntries[index]; }
 
 	/** Get added Dialog entries */
 	uint countDialog() const { return _conversationEntries.size(); }
-	ConversationLog &getDialog(uint index) { return _conversationEntries[index]; }
+	const ConversationLog &getDialog(uint index) const { return _conversationEntries[index]; }
 
 	/** Start recording speech lines for a dialog */
 	void openDialog(const Common::String &title, const Common::String &characterName, int32 characterId);