diff --git a/libsrc/occ/occgenmesh.cpp b/libsrc/occ/occgenmesh.cpp
index 8b00b684..9a714f8c 100644
--- a/libsrc/occ/occgenmesh.cpp
+++ b/libsrc/occ/occgenmesh.cpp
@@ -1110,7 +1110,9 @@ namespace netgen
               {
                 double s = s0 + j/(double) nsections * (s1-s0);
                 prop.SetParameter (s);
-                double curvature = prop.Curvature();
+                double curvature = 0;
+                if(prop.IsTangentDefined())
+                  curvature = prop.Curvature();
                 if(curvature> maxcur) maxcur = curvature;
 
                 if (curvature >= 1e99)