diff --git a/WeatherRoutingTool/ship/direct_power_boat.py b/WeatherRoutingTool/ship/direct_power_boat.py
index 7a87ac4..668ff8c 100644
--- a/WeatherRoutingTool/ship/direct_power_boat.py
+++ b/WeatherRoutingTool/ship/direct_power_boat.py
@@ -230,12 +230,15 @@ def get_apparent_wind(self, true_wind_speed, true_wind_angle):
             arg_arcsin = true_wind_speed[iang] * np.sin(np.radians(true_wind_angle[iang])) / apparent_wind_speed[
                 iang] * u.radian
 
-            # catch it if argument of arcsin is > 1 due to rounding issues but make sure to apply this only for
+            # catch it if argument of arcsin is > 1 and arcsin is < -1 due to rounding issues but make sure to apply this only for
             # rounding issues
             diff_to_one = arg_arcsin - 1 * u.radian
             if diff_to_one > 0:
                 assert diff_to_one < 0.000001 * u.radian
                 arg_arcsin = 1 * u.radian
+            elif (diff_to_minus_one := arg_arcsin + 1 * u.radian) < 0:
+                assert abs(diff_to_minus_one) < 0.000001 * u.radian
+                arg_arcsin = -1 * u.radian
 
             if apparent_wind_speed[iang] > 0:
                 apparent_wind_angle[iang] = np.arcsin(arg_arcsin.value) * u.radian