diff --git a/IV/slides-2021-03-29.txt b/IV/slides-2021-03-29.txt
index a12d1d3..85d49c6 100644
--- a/IV/slides-2021-03-29.txt
+++ b/IV/slides-2021-03-29.txt
@@ -78,11 +78,11 @@ linijinių objektų generalizacijai (Lietuvoje -- GDR50 ir GDR250 analogus)
 
 # Tolimesnis pritaikymas
 
-Sukurta algoritmo techninė realizacija atviro kodo GIS bus pradžia tolesniam jo
+- Sukurta algoritmo techninė realizacija atviro kodo GIS bus pradžia tolesniam jo
 pritaikymui kitiems gamtiniams objektams: ežerų kranto linija, jūrų,
 kontinentų, miškų ribos.
 
-Kadangi rezultatas bus techninė realizacija, o ne rašinėlis, tai suteikia
+- Kadangi rezultatas bus techninė realizacija, o ne rašinėlis, tai suteikia
 toliau galimybę vystyti sprendimą.
 
 # Demonstracija
diff --git a/IV/tests-integration.sql b/IV/tests-integration.sql
index 541d4a2..fbd7032 100644
--- a/IV/tests-integration.sql
+++ b/IV/tests-integration.sql
@@ -1,5 +1,8 @@
 \i wm.sql
 
-drop table if exists agg_rivers_wm;
-create table agg_rivers_wm (name text, way geometry);
-insert into agg_rivers_wm (name, way) select name, ST_SimplifyWM(way, true) from agg_rivers;
+drop table if exists debug_wm;
+create table debug_wm(name text, way geometry, props json);
+
+drop table if exists demo_wm;
+create table demo_wm (name text, i bigint, way geometry);
+insert into demo_wm (name, way) select name, ST_SimplifyWM(way, true) from agg_rivers;
diff --git a/IV/wm.sql b/IV/wm.sql
index 1873323..2adf2e9 100644
--- a/IV/wm.sql
+++ b/IV/wm.sql
@@ -276,7 +276,13 @@ begin
   fourpi = 4*radians(180);
   for i in 1..array_length(bends, 1) loop
     bend = bends[i];
-    select st_makepolygon(st_addpoint(bend, st_startpoint(bend))) into polygon;
+    if st_numpoints(bend) < 3 then
+      cmp = 0;
+      area = 0;
+      polygon = null;
+    else
+      select st_makepolygon(st_addpoint(bend, st_startpoint(bend))) into polygon;
+    end if;
     -- Compactness Index (cmp) is defined as "the ratio of the area of the
     -- polygon over the circle whose circumference length is the same as the
     -- length of the circumference of the polygon". I assume they meant the
@@ -285,15 +291,17 @@ begin
     -- 2. get polygon perimeter = u. Pretend it's our circle's circumference.
     -- 3. get A (area) of the circle from circumference u := (u^2)/(4*pi)
     -- 4. divide area by A: cmp = P/((u^2)*4*pi) = 4*pi*P/u^2
-    select st_area(polygon) into area;
-    select fourpi*area/(st_perimeter(polygon)^2) into cmp;
-    if cmp > 0 then
+    if polygon is not null then
+      select st_area(polygon) into area;
+      select fourpi*area/(st_perimeter(polygon)^2) into cmp;
+    end if;
+    if area > 0 then
       select (area*(0.75/cmp)) into adjsize;
     end if;
     if dbg then
       insert into debug_wm (name, way, props) values(
         'bend_attrs_' || i,
-        polygon,
+        bend,
         json_build_object('area', area, 'cmp', cmp, 'adjsize', adjsize)
       );
     end if;