diff --git a/PowerEditor/src/Parameters.h b/PowerEditor/src/Parameters.h
index 0834f5deb..4fce3886f 100644
--- a/PowerEditor/src/Parameters.h
+++ b/PowerEditor/src/Parameters.h
@@ -587,7 +587,7 @@ struct LangMenuItem final
 	LangMenuItem(LangType lt, int cmdID = 0, const std::wstring& langName = TEXT("")):
 	_langType(lt), _cmdID(cmdID), _langName(langName){};
 
-	bool operator<(const LangMenuItem& rhs)
+	bool operator<(const LangMenuItem& rhs) const
 	{
 		std::wstring lhs_lang(this->_langName.length(), ' '), rhs_lang(rhs._langName.length(), ' ');
 		std::transform(this->_langName.begin(), this->_langName.end(), lhs_lang.begin(), towlower);