diff --git a/fatamorgana/basic.py b/fatamorgana/basic.py
index 4db5ba0..7619b27 100644
--- a/fatamorgana/basic.py
+++ b/fatamorgana/basic.py
@@ -1302,38 +1302,25 @@ def read_point_list(stream: io.BufferedIOBase) -> List[List[int]]:
     """
     list_type = read_uint(stream)
     list_len = read_uint(stream)
+    #TODO: Implicit close point for 1del
     if list_type == 0:
         points = []
-        dx, dy = 0, 0
         for i in range(list_len):
             point = [0, 0]
-            n = read_sint(stream)
+            n = read_uint(stream)
             if n == 0:
                 raise InvalidDataError('Zero-sized 1-delta')
             point[i % 2] = n
             points.append(point)
-            if i % 2:
-                dy += n
-            else:
-                dx += n
-        points.append([-dx, 0])
-        points.append([0, -dy])
     elif list_type == 1:
         points = []
-        dx, dy = 0, 0
         for i in range(list_len):
             point = [0, 0]
-            n = read_sint(stream)
+            n = read_uint(stream)
             if n == 0:
                 raise Exception('Zero-sized 1-delta')
             point[(i + 1) % 2] = n
             points.append(point)
-            if i % 2:
-                dx += n
-            else:
-                dy += n
-        points.append([0, -dy])
-        points.append([-dx, 0])
     elif list_type == 2:
         points = [ManhattanDelta.read(stream).as_list() for _ in range(list_len)]
     elif list_type == 3:
diff --git a/fatamorgana/records.py b/fatamorgana/records.py
index f76682e..aabc3b4 100644
--- a/fatamorgana/records.py
+++ b/fatamorgana/records.py
@@ -18,7 +18,7 @@ import zlib
 import io
 import logging
 import pprint
-from warnings import warn
+
 from .basic import AString, NString, repetition_t, property_value_t, real_t, \
         ReuseRepetition, OffsetTable, Validation, read_point_list, read_property_value, \
         read_bstring, read_uint, read_sint, read_real, read_repetition, read_interval, \
@@ -1630,7 +1630,7 @@ class Polygon(Record):
 
         if point_list is not None:
             if len(point_list) < 3:
-                warn('Polygon with < 3 points')
+                raise InvalidDataError('Polygon with < 3 points')
 
     def merge_with_modals(self, modals: Modals):
         adjust_coordinates(self, modals, 'geometry_x', 'geometry_y')