diff --git a/CHANGELOG.md b/CHANGELOG.md
index 85ee170ee1..76ef957565 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,7 @@
 # Changelog for releases
 
 ## v1.0.0
-- asdf
+- `orientation_to_neighbor` 45, 135, 225, and 315 degrees are all considered `east_west`. Previously, 45 and 225 degrees were considered `north_south`.
 
 ## v0.0.0
 - Initial release
diff --git a/naturf/nodes.py b/naturf/nodes.py
index 770359abdd..44e9aa6abe 100644
--- a/naturf/nodes.py
+++ b/naturf/nodes.py
@@ -301,9 +301,9 @@ def orientation_to_neighbor(angle_in_degrees_to_neighbor: pd.Series) -> pd.Serie
                 (((Settings.SOUTHEAST_DEGREES <= angle_in_degrees_to_neighbor) &
                     (angle_in_degrees_to_neighbor <= Settings.DEGREES_IN_CIRCLE))
                 | ((Settings.START_OF_CIRCLE_DEGREES <= angle_in_degrees_to_neighbor) &
-                    (angle_in_degrees_to_neighbor < Settings.NORTHEAST_DEGREES)))
+                    (angle_in_degrees_to_neighbor <= Settings.NORTHEAST_DEGREES)))
                 | ((Settings.NORTHWEST_DEGREES <= angle_in_degrees_to_neighbor) &
-                    (angle_in_degrees_to_neighbor < Settings.SOUTHWEST_DEGREES)),
+                    (angle_in_degrees_to_neighbor <= Settings.SOUTHWEST_DEGREES)),
                 "east_west",
                 "north_south"
             ),
diff --git a/naturf/tests/test_nodes.py b/naturf/tests/test_nodes.py
index 9e49e5ea4c..3c8739d8f7 100644
--- a/naturf/tests/test_nodes.py
+++ b/naturf/tests/test_nodes.py
@@ -11,7 +11,7 @@
 
 
 from naturf.driver import Model
-from naturf.nodes import angle_in_degrees_to_neighbor
+import naturf.nodes as nodes
 
 
 class TestNodes(unittest.TestCase):
@@ -70,7 +70,7 @@ class TestCase:
             ]
 
         for case in testcases:
-            actual = angle_in_degrees_to_neighbor(gpd.GeoSeries(case.target_input), gpd.GeoSeries(case.neighbor_input))
+            actual = nodes.angle_in_degrees_to_neighbor(gpd.GeoSeries(case.target_input), gpd.GeoSeries(case.neighbor_input))
             expected = pd.Series(case.expected)
             pd.testing.assert_series_equal(
                 expected,
@@ -80,6 +80,32 @@ class TestCase:
                 ),
             )
 
+    def test_orientation_to_neighbor(self):
+        """Test that the function `orientation_to_neighbor` returns either `east_west` or `north_south` correctly."""
+        @dataclass
+        class TestCase:
+            name: str
+            input: List[int]
+            expected: List[int]
+
+        east_west = "east_west"
+        north_south = "north_south"
+
+        testcases = [
+            TestCase(name="zero_degrees", input=[0.0, -0.0], expected=[east_west, east_west]),
+            TestCase(name="north_south", input=[90, 270], expected=[north_south, north_south]),
+            TestCase(name="east_west", input=[45, 135, 225, 315, 360], expected=[east_west, east_west, east_west, east_west, east_west]),
+            ]
+
+        for case in testcases:
+            actual = nodes.orientation_to_neighbor(pd.Series(case.input))
+            expected = pd.Series(case.expected)
+            pd.testing.assert_series_equal(
+                expected,
+                actual,
+                f"failed test {case.name} expected {expected}, actual {actual}"
+            )
+
 
 if __name__ == '__main__':
-    unittest.main()
+    unittest.main()
\ No newline at end of file