diff --git a/src/strings_func.h b/src/strings_func.h
--- a/src/strings_func.h
+++ b/src/strings_func.h
@@ -96,6 +96,7 @@ static inline void CopyOutDParam(uint64 
 }
 
 extern DynamicLanguages _dynlang; // defined in strings.cpp
+extern TextDirection _current_text_dir; ///< Text direction of the currently selected language
 
 bool ReadLanguagePack(int index);
 void InitializeLanguagePacks();