diff --git a/src/bezier_surface.scad b/src/bezier_surface.scad
index ccc36177..e1889149 100644
--- a/src/bezier_surface.scad
+++ b/src/bezier_surface.scad
@@ -10,10 +10,10 @@
 
 function bezier_surface(t_step, ctrl_pts) =
     let(pts =  [
-        for(i = [0:len(ctrl_pts) - 1]) 
+        for(i = 0; i < len(ctrl_pts); i = i + 1)
             bezier_curve(t_step, ctrl_pts[i])
     ]) 
-    [for(x = [0:len(pts[0]) - 1]) 
+    [for(x = 0; x < len(pts[0]); x = x + 1)
         bezier_curve(t_step,  
                 [for(y = [0:len(pts) - 1]) pts[y][x]]
         )