diff --git a/src/aare/gui/widgets/camera_image.py b/src/aare/gui/widgets/camera_image.py
index 27ee8a54..14b8a0dd 100644
--- a/src/aare/gui/widgets/camera_image.py
+++ b/src/aare/gui/widgets/camera_image.py
@@ -1354,7 +1354,13 @@ class SampleCameraImageLabel(QGraphicsView):
 
     def wheelEvent(self, event: QWheelEvent):
         if not self.wheel_event_timer.isActive():
-            delta_y = event.angleDelta().y()
+            # Qt's xcb/windows platform plugins swap wheel axes while Alt is held,
+            # so a vertical scroll lands in angleDelta().x() and y() is 0. Without
+            # this fallback, copysign(_, 0) is always positive and Alt+wheel
+            # exposure can only ever increase.
+            delta_y = event.angleDelta().y() or event.angleDelta().x()
+            if delta_y == 0:
+                return
             match self._state:
                 case SampleCameraImageState.BEAM_MARKING:
                     if event.modifiers() & Qt.KeyboardModifier.AltModifier: