diff --git a/EGnStringUtils.h b/EGnStringUtils.h
index 8e51f5b..34002ac 100644
--- a/EGnStringUtils.h
+++ b/EGnStringUtils.h
@@ -245,7 +245,7 @@ const std::string ToString( const int (&nVal)[size], int nPrec = 1)
 inline const std::string
 ToString( bool bVal)
       { return std::string( ( bVal ? "1" : "0")) ; }
-EGN_EXPORT const std::string ToString( double dVal, int nPrec = 6) ;
+EGN_EXPORT const std::string ToString( double dVal, int nPrec = 6, int* pnErr = nullptr) ;
 template <size_t size>
 const std::string ToString( const double (&dVal)[size], int nPrec = 6)
       { std::string sDest ; sDest.reserve( 14 * size) ;