diff --git a/las_manipulation.py b/las_manipulation.py
index 9a44b67..7fc5357 100644
--- a/las_manipulation.py
+++ b/las_manipulation.py
@@ -350,8 +350,11 @@ def polygon_wave_runup(xyz_1m, direction, shp_name, set_check_value, distance_ch
     #making the cropping shapefile
     #print('making the crop polygon')
 
+    # Simplify polygon to remove invalid geometry
+    geom = Polygon(for_shape).simplify(10)
+
     # Export polygon as shapefile
-    df = gpd.GeoDataFrame(geometry=[Polygon(for_shape)])
+    df = gpd.GeoDataFrame(geometry=[geom])
     df.crs = {'init': 'epsg:283{}'.format(zone), 'no_defs': True}
     df.to_file(shp_name, driver='ESRI Shapefile')