diff --git a/EGkCurveArc.h b/EGkCurveArc.h
index 6e7d4fc..a4b2f4f 100644
--- a/EGkCurveArc.h
+++ b/EGkCurveArc.h
@@ -53,6 +53,7 @@ class __declspec( novtable) ICurveArc : public ICurve
       virtual bool InvertN( void) = 0 ;
       virtual bool ChangeRadius( double dNewRadius) = 0 ;
       virtual bool ChangeDeltaN( double dNewDeltaN) = 0 ;
+      virtual bool ChangeAngCenter( double dNewAngCenDeg) = 0 ;
       virtual bool ChangeStartPoint( double dU) = 0 ;
       virtual bool ExtendedOffset( double dDist, int nType = OFF_FILLET) = 0 ;
       virtual bool ToExplementary( void) = 0 ;