diff --git a/gerber/primitives.py b/gerber/primitives.py
index a031199..b24b6c3 100644
--- a/gerber/primitives.py
+++ b/gerber/primitives.py
@@ -1669,9 +1669,12 @@ class Slot(Primitive):
     @property
     def bounding_box(self):
         if self._bounding_box is None:
-            ll = tuple([c - self.diameter / 2. for c in self.position])
-            ur = tuple([c + self.diameter / 2. for c in self.position])
-            self._bounding_box = ((ll[0], ur[0]), (ll[1], ur[1]))
+            radius = self.diameter / 2.
+            min_x = min(self.start[0], self.end[0]) - radius
+            max_x = max(self.start[0], self.end[0]) + radius
+            min_y = min(self.start[1], self.end[1]) - radius
+            max_y = max(self.start[1], self.end[1]) + radius
+            self._bounding_box = ((min_x, max_x), (min_y, max_y))
         return self._bounding_box
 
     def offset(self, x_offset=0, y_offset=0):
diff --git a/gerber/tests/test_primitives.py b/gerber/tests/test_primitives.py
index 2fe5a4b..b932297 100644
--- a/gerber/tests/test_primitives.py
+++ b/gerber/tests/test_primitives.py
@@ -1343,3 +1343,17 @@ def test_drill_equality():
     assert_equal(d, d1)
     d1 = Drill((2.54, 25.4), 254.2)
     assert_not_equal(d, d1)
+
+
+def test_slot_bounds():
+    """ Test Slot primitive bounding box calculation
+    """
+    cases = [((0, 0), (1, 1), ((-1, 2), (-1, 2))),
+             ((-1, -1), (1, 1), ((-2, 2), (-2, 2))),
+             ((1, 1), (-1, -1), ((-2, 2), (-2, 2))),
+             ((-1, 1), (1, -1), ((-2, 2), (-2, 2))), ]
+
+    for start, end, expected in cases:
+        s = Slot(start, end, 2.0)
+        assert_equal(s.bounding_box, expected)
+