diff --git a/EGkSurfBezier.h b/EGkSurfBezier.h
index ec8d32d..ee3147e 100644
--- a/EGkSurfBezier.h
+++ b/EGkSurfBezier.h
@@ -101,6 +101,7 @@ class __declspec( novtable) ISurfBezier : public ISurf
       virtual bool CreateByPointCurve( const Point3d& pt, const ICurve* pCurve) = 0 ;
       virtual bool CreateByTwoCurves( const ICurve* pCurve1, const ICurve* pCurve2, int nType) = 0 ;
       virtual bool CreateBySetOfCurves( const ICURVEPOVECTOR& vCrvBez, bool bReduceToDeg3 = true) = 0 ;
+      virtual bool RemoveCollapsedSpans() = 0 ;
 } ;
 
 //-----------------------------------------------------------------------------