diff --git a/EGkCurveComposite.h b/EGkCurveComposite.h
index 753f0a9..539c7c8 100644
--- a/EGkCurveComposite.h
+++ b/EGkCurveComposite.h
@@ -50,7 +50,7 @@ class __declspec( novtable) ICurveComposite : public ICurve
       virtual bool RemoveJoint( int nU) = 0 ;
       virtual bool ArcsToBezierCurves( void) = 0 ;
       virtual bool ArcsBezierCurvesToArcsPerpExtr( double dLinTol, double dAngTolDeg) = 0 ;
-      virtual bool MergeCurves( double dLinTol, double dAngTolDeg, bool bStartEnd = true) = 0 ;
+      virtual bool MergeCurves( double dLinTol, double dAngTolDeg, bool bStartEnd = true, bool bNeedSameProp = false) = 0 ;
       virtual bool RemoveUndercutOnY( double dLinTol, double dAngTolDeg) = 0 ;
       virtual bool IsACircle( double dLinTol, Point3d& ptCen, Vector3d& vtN, double& dRad, bool& bCCW) const = 0 ;
       virtual bool SetCurveTempProp( int nCrv, int nProp) = 0 ;