diff --git a/src/evdev.c b/src/evdev.c
index b09bb989..9c53e327 100644
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -976,7 +976,8 @@ evdev_device_get_id_vendor(struct evdev_device *device)
 }
 
 void
-evdev_device_calibrate(struct evdev_device *device, float calibration[6])
+evdev_device_calibrate(struct evdev_device *device,
+		       const float calibration[6])
 {
 	device->abs.apply_calibration = 1;
 	memcpy(device->abs.calibration, calibration, sizeof device->abs.calibration);
diff --git a/src/evdev.h b/src/evdev.h
index f1ccdc29..6aa98f54 100644
--- a/src/evdev.h
+++ b/src/evdev.h
@@ -159,7 +159,8 @@ unsigned int
 evdev_device_get_id_vendor(struct evdev_device *device);
 
 void
-evdev_device_calibrate(struct evdev_device *device, float calibration[6]);
+evdev_device_calibrate(struct evdev_device *device,
+		       const float calibration[6]);
 
 int
 evdev_device_has_capability(struct evdev_device *device,