diff --git a/CGAL_ImageIO/include/CGAL/Image_3.h b/CGAL_ImageIO/include/CGAL/Image_3.h
index b22801307aa..a6584d0fad9 100644
--- a/CGAL_ImageIO/include/CGAL/Image_3.h
+++ b/CGAL_ImageIO/include/CGAL/Image_3.h
@@ -517,9 +517,7 @@ Image_3::labellized_trilinear_interpolation
     Image_word_type iwt = labels[i];
     const double r = 
       trilinear_interpolation<Image_word_type,double,Coord_type>(
-        x, y, z, 0., indicator_factory.indicator(iwt));
-    CGAL_assertion(r >= 0.);
-    CGAL_assertion(r <= 1.);
+        x, y, z, value_outside, indicator_factory.indicator(iwt));
 
     if(r > best_value) {
       best = iwt;