diff --git a/cheetah/accelerator.py b/cheetah/accelerator.py
index 6e62c887..582063bb 100644
--- a/cheetah/accelerator.py
+++ b/cheetah/accelerator.py
@@ -40,6 +40,8 @@ class Element:
     Base class for elements of particle accelerators.
 
     :param name: Unique identifier of the element.
+    :param is_active: Whether the element is active or not. This can have different
+        meanings depending on the element type.
     :param device: Device to move the beam's particle array to. If set to `"auto"` a
         CUDA GPU is selected if available. The CPU is used otherwise.
     """
@@ -50,7 +52,9 @@ class Element:
     device: str = "auto"
     length: float = 0
 
-    def __init__(self, name: Optional[str] = None, device: str = "auto") -> None:
+    def __init__(
+        self, name: Optional[str] = None, is_active: bool = False, device: str = "auto"
+    ) -> None:
         global ELEMENT_COUNT
         if name is not None:
             self.name = name
@@ -931,6 +935,7 @@ class Aperture(Element):
     :param y_max: half size vertical offset in [m]
     :param shape: Shape of the aperture. Can be "rectangular" or "elliptical".
     :param name: Unique identifier of the element.
+    :param is_active: If the aperture actually blocks particles.
     """
 
     x_max: float = np.inf
@@ -943,6 +948,7 @@ def __init__(
         y_max: float = np.inf,
         shape: Literal["rectangular", "elliptical"] = "rectangular",
         name: Optional[str] = None,
+        is_active: bool = True,
         **kwargs,
     ) -> None:
         super().__init__(name, **kwargs)
@@ -950,6 +956,7 @@ def __init__(
         self.x_max = x_max
         self.y_max = y_max
         self.shape = shape
+        self.is_active = is_active
 
         self.lost_particles = None
 
diff --git a/test/test_compare_ocelot.py b/test/test_compare_ocelot.py
index f105e414..c9074d72 100644
--- a/test/test_compare_ocelot.py
+++ b/test/test_compare_ocelot.py
@@ -70,12 +70,15 @@ def test_aperture():
     cheetah_segment = cheetah.Segment(
         [
             cheetah.Aperture(
-                x_max=2e-4, y_max=2e-4, shape="rectangular", name="aperture"
-            ),  # TODO: is_active on init
+                x_max=2e-4,
+                y_max=2e-4,
+                shape="rectangular",
+                name="aperture",
+                is_active=True,
+            ),
             cheetah.Drift(length=0.1),
         ]
     )
-    cheetah_segment.aperture.is_active = True
     outgoing_beam = cheetah_segment.track(incoming_beam)
 
     # Ocelot
@@ -103,12 +106,15 @@ def test_aperture_elliptical():
     cheetah_segment = cheetah.Segment(
         [
             cheetah.Aperture(
-                x_max=2e-4, y_max=2e-4, shape="elliptical", name="aperture"
-            ),  # TODO: is_active on init
+                x_max=2e-4,
+                y_max=2e-4,
+                shape="elliptical",
+                name="aperture",
+                is_active=True,
+            ),
             cheetah.Drift(length=0.1),
         ]
     )
-    cheetah_segment.aperture.is_active = True
     outgoing_beam = cheetah_segment.track(incoming_beam)
 
     # Ocelot