diff --git a/Inst_eddies/get_1_outerm.f90 b/Inst_eddies/get_1_outerm.f90
index b60a9b00eea5b784a87cbd655cd62a337a1db838..ce73601d0d1d0475be60f18dc284bbc7a682a59c 100644
--- a/Inst_eddies/get_1_outerm.f90
+++ b/Inst_eddies/get_1_outerm.f90
@@ -29,7 +29,8 @@ contains
     ! abs(ediff1d(cont_list_proj(:n_cont)%ssh)) is in descending
     ! order. (See notes for a proof.) On return, n_cont == 1 means we
     ! have only found one good contour at innermost_level_2 and it has
-    ! sufficient area.
+    ! sufficient area. On return, n_cont == 0 .eqv. out_cont ==
+    ! null_polyline().
 
     ! Method: dichotomy on level of ssh.
 
diff --git a/Inst_eddies/set_contours.f90 b/Inst_eddies/set_contours.f90
index 2d12b75ee5779d4c1f1518a4092c5376e2459786..d7477c0d2ddb0b79a6879dadeecf48288f1d9b22 100644
--- a/Inst_eddies/set_contours.f90
+++ b/Inst_eddies/set_contours.f90
@@ -100,6 +100,7 @@ contains
     ! Done with outermost contour, now let us take care of the
     ! max-speed contour.
     if (out_cont%closed) then
+       ! assert n_cont >= 1
        ! {begin} Restrict the field to the outermost contour:
 
        llc = floor((corner_whole - corner) / step &