diff --git a/EXE_GdbGetSurf.cpp b/EXE_GdbGetSurf.cpp
index 0af254a..15a54ad 100644
--- a/EXE_GdbGetSurf.cpp
+++ b/EXE_GdbGetSurf.cpp
@@ -1866,7 +1866,7 @@ ExeShowSurfBezierControlPoints( int nSrfId, int nDestGrpId, int* pnCount)
    VERIFY_GEOMDB( pGeomDB, GDB_ID_NULL)
    // recupero la superficie di bezier
    IGeoObj* pGeoObj = pGeomDB->GetGeoObj( nSrfId) ;
-   if ( pGeoObj->GetType() != SRF_BEZIER)
+   if ( pGeoObj == nullptr  ||  pGeoObj->GetType() != SRF_BEZIER)
       return GDB_ID_NULL ;
    // recupero il riferimento della superficie
    Frame3d frSurf ;