diff --git a/examples/check.ctl b/examples/check.ctl
index b8d114c..d491ed3 100644
--- a/examples/check.ctl
+++ b/examples/check.ctl
@@ -318,33 +318,34 @@
 ; define a simple geometry with inversion and z-mirror
 (set! geometry-lattice
   (make lattice (size 1 1 1) (basis1 1 0 0) (basis2 0 1 0) (basis3 0 0 1)))
-(set! geometry 
+(set! geometry
   (list (make sphere (center 0 0 0) (radius 0.25) (material (make dielectric (epsilon 13) )))))
 
 ; compare inversion eigenvalues at k = [1,1,1]/2 against precomputed values
 (set! k-points (list (vector3 0.5 0.5 0.5)))                              ; little group includes inversion
-(define W (matrix3x3 (vector3 -1 0 0) (vector3 0 -1 0) (vector3 0 0 -1))) ; inversion as operation {W|w}
-(define w (vector3 0 0 0))
-
-(run)
-(define symeigs-inv (compute-symmetries W w))
-(check-almost-equal (map real-part symeigs-inv) '(+1 +1 +1 -1 -1 -1))
-(check-almost-equal (map imag-part symeigs-inv) '( 0  0  0  0  0  0))
-
-; compare with run-zeven and run-zodd at k = 0 [must be 0 due to https://github.com/NanoComp/mpb/issues/114]
-(set! k-points (list (vector3 0 0 0)))
-(define mz (matrix3x3 (vector3 1 0 0)  (vector3 0 1 0)  (vector3 0 0 -1)))
-
-(run-zeven) ; even z-parity check
-(define symeigs-zeven (compute-symmetries mz w))
-(check-almost-equal (map real-part symeigs-zeven) '(+1 +1 +1 +1 +1 +1))
-(check-almost-equal (map imag-part symeigs-zeven) '( 0  0  0  0  0  0))
-
-(run-zodd) ; odd z-parity check
-(define symeigs-zodd (compute-symmetries mz w))
-(check-almost-equal (map real-part symeigs-zodd) '(-1 -1 -1 -1 -1 -1))
-(check-almost-equal (map imag-part symeigs-zodd) '( 0  0  0  0  0  0))
 
+; inversion as operation {W|w}
+(let ((W (matrix3x3 (vector3 -1 0 0) (vector3 0 -1 0) (vector3 0 0 -1)))
+      (w (vector3 0 0 0)))
+  (run)
+  (define symeigs-inv (compute-symmetries W w))
+  (check-almost-equal (map real-part symeigs-inv) '(+1 +1 +1 -1 -1 -1))
+  (check-almost-equal (map imag-part symeigs-inv) '( 0  0  0  0  0  0))
+
+  ; compare with run-zeven and run-zodd at k = 0 [must be 0 due to https://github.com/NanoComp/mpb/issues/114]
+  (set! k-points (list (vector3 0 0 0)))
+  (define mz (matrix3x3 (vector3 1 0 0)  (vector3 0 1 0)  (vector3 0 0 -1)))
+
+  (run-zeven) ; even z-parity check
+  (define symeigs-zeven (compute-symmetries mz w))
+  (check-almost-equal (map real-part symeigs-zeven) '(+1 +1 +1 +1 +1 +1))
+  (check-almost-equal (map imag-part symeigs-zeven) '( 0  0  0  0  0  0))
+
+  (run-zodd) ; odd z-parity check
+  (define symeigs-zodd (compute-symmetries mz w))
+  (check-almost-equal (map real-part symeigs-zodd) '(-1 -1 -1 -1 -1 -1))
+  (check-almost-equal (map imag-part symeigs-zodd) '( 0  0  0  0  0  0))
+) ; let
 
 ) ; begin
 ) ; if (not (using-mpi?))