diff --git a/src/StdString.h b/src/StdString.h
index fb7113c03d..43c23b9c61 100644
--- a/src/StdString.h
+++ b/src/StdString.h
@@ -769,6 +769,10 @@ public:
 	const CT& operator[](long unsigned int nIdx) const {
 	  return MYBASE::operator[](static_cast<MYSIZE>(nIdx));
 	}
+	
+	const CT& operator[](long long unsigned int nIdx) const {
+	  return MYBASE::operator[](static_cast<MYSIZE>(nIdx));
+	}
 #ifndef SS_NO_IMPLICIT_CASTS
 	operator const CT*() const
 	{