diff --git a/CalcPocketing.cpp b/CalcPocketing.cpp
index 834e4ad..fc4d685 100644
--- a/CalcPocketing.cpp
+++ b/CalcPocketing.cpp
@@ -7020,7 +7020,7 @@ CalcZigZag( const ISurfFlatRegion* pSfrZigZag, const PocketParams& PockParams, I
             if ( vvSec[nI + 1][nA].bActive)
                continue ;
             PtrOwner<ICurveLine> pLA( CreateCurveLine()) ;
-            if ( IsNull( pLA)  ||  pLA->Set( vvSec[nI + 1][nA].ptS, vvSec[nI + 1][nA].ptE))
+            if ( IsNull( pLA)  ||  ! pLA->Set( vvSec[nI + 1][nA].ptS, vvSec[nI + 1][nA].ptE))
                return false ;
             vLineAbove.emplace_back( Release( pLA)) ;
          }